Aftab Ahamed - Academia.edu (original) (raw)

Papers by Aftab Ahamed

Research paper thumbnail of Embryonic development following microsurgical restoration of the diploid constitution in the human tripronuclear zygote

Fertility and Sterility, 2015

Research paper thumbnail of Conjugation of laccase from the white rot fungus Trametes versicolor to chitosan and its utilization for the elimination of triclosan

Bioresource Technology, 2011

A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-eth... more A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) as the cross-linking agent. Laccase-chitosan conjugation strategies were tested using different molar ratios of glucosamine monomer/protein with different molar excess ratios of EDC relative to laccase. Immobilization techniques were developed to improve the stability against thermal and chemical denaturation, storage and reusability of this biocatalyst. The conjugation resulted in a solid biocatalyst with an apparent laccase activity of ±626 U/g, 12 and 60 folds higher in the conjugation efficiency of biocatalyst relative to the immobilized and free laccase activity respectively when compared with zero EDC/laccase ratio used in conjugation solution. The conjugated laccases formed successfully eliminated the emerging pollutant triclosan (TCS) from aqueous solutions, having a higher potential to transform TCS than free laccase. UPLC-QTOF results indicate the formation of TCS oligomers. Furthermore, they are the first evidence of direct dechlorination of TCS mediated by the oxidative action of laccases.

Research paper thumbnail of Efficiency of food and dietary water utilisation and cocoon conversion in the new multivoltine breeds of silkworm, Bombyx mori L

Journal of Insect Science, 2002

Food and dietary water intake and their utilization in the new multivoltine breeds of silkworm Bo... more Food and dietary water intake and their utilization in the new multivoltine breeds of silkworm Bombyx marl L., viz. BL - 23, BL -24 and PM as control ted ad Ilbitum on M 5 mulberry leaf during 5th instar at the temperature of 26 ′ 1°C and 75 ′ 5% R.H. are reported. In the new multivoltine breeds, the larval duration was significantly shorter from 3.25 (BL - 23) to 3.50 (BL -24) days than the Pure Mysore race. The decrement in dry food consumed, food assimilated, assimilation efficiency, food oxidized, feeding rete, assimilation rate and metabolic rate was noticed in the new breeds when compared with the control. However, the conversion efficiencies (K 1 & K 2 ) and water retention efficiency were significantly higher in the new breeds. Due to higher conversion efficiencies, the larval biomass accumulation and cocoon conversion efficiencies were higher in the new breeds. The causative factors responsible for these changes have been discussed.

Research paper thumbnail of Facile Extraction of Wheat Straw by Deep Eutectic Solvent (DES) to Produce Lignin Nanoparticles

ACS Sustainable Chemistry & Engineering

A detailed investigation of choline chloride-lactic acid (ChCl-LA)-based deep eutectic solvent (D... more A detailed investigation of choline chloride-lactic acid (ChCl-LA)-based deep eutectic solvent (DES) extraction of lignin nanoparticles from herbaceous biomass (wheat straw) was conducted. It was found that DES can extract high purity lignin (up to 94.8%) with a high yield (up to 81.5% from air-dried samples and 85.9% from oven-dried samples) from wheat straw. The cleavages of ether bonds in lignin, as well as the linkages between lignin and hemicelluloses during DES treatments at different conditions, were analyzed. The effects of reaction time, treatment temperature and water content in wheat straw on lignin yield, purity, and chemical structure were determined. The water content in biomass was found to affect the hydrogen bond interaction between lignin and DES, which was a key factor influencing the lignin extraction yield and chemical properties of separated lignin. The lignin extracted from wheat straw by DES consists of well-dispersed nanoparticles with a narrow size distribution peaking at 70–90 nm. The mechanism of ChCl-LA-based DES depolymerization and extraction of lignin from wheat straw is discussed.

Research paper thumbnail of Kinetic understanding of nitrogen supply condition on biosynthesis of polyhydroxyalkanoate from benzoate by Pseudomonas putida KT2440

Bioresource Technology

Nitrogen supply is critical to the synthesis of intracellular PHA in various bacteria. However, t... more Nitrogen supply is critical to the synthesis of intracellular PHA in various bacteria. However, the specific role of the nitrogen in synthesizing PHA from benzoate, a lignin model compound use for the study of bacteria catabolism of aromatics, is still not clear. In this study, two culture conditions were maintained for Pseudomonas putida KT2440 to produce PHA using benzoate as a carbon source. Under nitrogen-limited and surplus conditions, the accumulation of PHA was to 37.3% and 0.25% of cell dry weight, respectively. A model fit to the kinetics of biomass growth and PHA accumulation showed good agreement with data. GC-MS and NMR showed that PHA contained six hydroxyl fatty acid monomers under nitrogen-limited conditions, while two monomers were identified under nitrogen surplus conditions. The average molecular weight of PHA increased after the nitrogen source was exhausted. These results provide a promising strategy for optimization of lignin to PHA yields.

Research paper thumbnail of Cocoon Yield Pattern and Analysis of Water, Soil and Leaves from Mulberry Gardens Irrigated with Polluted Water Around Bangalore, India

Sericulturists in the vicinity of Bangalore city irrigate their mulberry gardens with Vrishabhava... more Sericulturists in the vicinity of Bangalore city irrigate their mulberry gardens with Vrishabhavathy stream water, which is polluted with domestic and industrial wastes from the city. To investigate the effect of pollutants on silkworm crops, a detailed field survey was conducted to study the cocoon yield pattern of the crops raised on mulberry irrigated with wastewater as against irrigation by bore/open wells. The villages along the stream were grouped into five test batches at about a distance of km from each other. The seasonal yield data with relevant information were collected through questionnaires from 117 rearers using stream water and 35 rearers using bore/open wells, the latter serving as control group. The average yield for 100 layings was 46 to 57 kg in the control group whereas in test groups, it ranged between 34 to 51 kg in the first test group and 22 to 38 kg in the rest. The difference in yield was kg depending on the season between control and test batches. In summ...

Research paper thumbnail of 2015 - Ahring et al. - Making lignin accessible for anaerobic digestion by wet-explosion pretreatment

The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosi... more The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosion pretreatment promotes lignin solubility. 4.5 times higher methane yield observed as a result of the pretreatment. 44.4% lignin in pretreated material was actually converted in the AD process. Aliphatic compounds formed in the pretreatment were utilized by microbes.

Research paper thumbnail of Making lignin accessible for anaerobic digestion by wet-explosion pretreatment

Bioresource Technology, 2014

The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosi... more The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosion pretreatment promotes lignin solubility. 4.5 times higher methane yield observed as a result of the pretreatment. 44.4% lignin in pretreated material was actually converted in the AD process. Aliphatic compounds formed in the pretreatment were utilized by microbes.

Research paper thumbnail of Production of hydrocarbons by Aspergillus carbonarius ITEM 5010

Fungal Biology, 2015

Lignocellulosic biomass a b s t r a c t

Research paper thumbnail of Culture-Based Strategies for Reduction of Protease Activity in Filtrates from Aspergillus niger NRRL-3

World Journal of Microbiology and Biotechnology, 2005

While Aspergillus strains are also being considered as potential hosts for production of extracel... more While Aspergillus strains are also being considered as potential hosts for production of extracellular heterologous proteins, the proteases produced by the host are highly problematic in that they typically modify and degrade the recombinant proteins. Culture-based approaches for minimization of protease activity in culture supernatants of Aspergillus niger NRRL-3 included reduction or elimination of peptide nitrogen in the medium, preferential use of a defined salts medium rather than a non-peptide nitrogen medium containing yeast-nitrogen base, supplementation of the medium with carboxymethylcellulose and cultivation at pH 6.5 rather than 7.5. In general, increased proteolytic activity was observed after maximum biomass was observed and biomass was declining suggesting the majority of protease activity was released by cell lysis. Carboxymethylcellulose shifted mycelial morphology from pelleted to filamentous. Mycelium lysis in the centre of pellets, with resultant release of intracellular proteases, would explain why filamentous cultures exhibited much lower proteolytic activity than pelleted cultures.

Research paper thumbnail of Incorporation of pepstatin into culture media for reduction of protease activity in filtrates from Aspergillus niger NRRL-3

Process Biochemistry, 2006

Aspergillus species have been used in different industrial applications including extracellular e... more Aspergillus species have been used in different industrial applications including extracellular enzyme production and as potential hosts for recombinant heterologous proteins production because of their excellent growth and fermentation properties. However, recombinant protein production levels are typically low due to the impact of Aspergillus proteases in modifying and degrading the heterologous proteins, especially in the extracellular medium. The potential of using the protease inhibitor pepstatin in filamentous Aspergillus niger culture was investigated in this study. The majority of protease activity was released into the medium as biomass content decreases after maximum biomass concentration was attained and a low concentration of pepstatin effectively inhibited the extracellular protease activity to an extent of 80-90%. The effectiveness of pepstatin in inhibiting the majority of protease activity was further demonstrated in media supplemented with both non-peptide and peptidecontaining nitrogen sources. Pepstatin addition had no effect on microbial growth. Dilution of the culture filtrate released inhibition, indicating that pepstatin did not have a notable effect on protease production and that inhibition was reversible. #

Research paper thumbnail of Chymostatin can combine with pepstatin to eliminate extracellular protease activity in cultures of Aspergillus niger NRRL-3

Journal of Industrial Microbiology & Biotechnology, 2007

Aspergillus strains are being considered as potential hosts for recombinant heterologous protein ... more Aspergillus strains are being considered as potential hosts for recombinant heterologous protein production because of their excellent extracellular enzyme production characteristics. However, Aspergillus proteases are problematic in that they modify and degrade the heterologous proteins in the extracellular medium. In previous studies we observed that media adjustments and maintenance of a filamentous morphology greatly reduced protease activity and that a low concentration of the aspartic protease inhibitor pepstatin inhibited the latter protease activity to the extent of approximately 90%. In this paper we report that when the serine protease inhibitor chymostatin is used in combination with pepstatin 99-100% of total protease activity in Aspergillus cultures is inhibited. In protease assays a concentration of 30 microM chymostatin combined with 0.075 microM pepstatin was required for maximum inhibition. Inhibitor concentrations of chymostatin and pepstatin of 120 and 0.3 microM, respectively, when added to Aspergillus cultures, has no significant effect on biomass production, glucose utilization or culture pH pattern. The potential of using these protease inhibitors in cultures of recombinant Aspergillus strains producing heterologous proteins will now be investigated to determine if the previously observed recombinant protein denaturing effects of Aspergillus proteases can be negated.

Research paper thumbnail of Effect of Oral Administration of Sodium Fluoride on Food and Water Utilisation in Silkworm, Bombyx mori L

International Journal of Tropical Insect Science, 1999

Page 1. Insect Sci. Applic. Vol. 19, No. 2/3, pp. 193-198, 1999 Printed in Kenya. All rights rese... more Page 1. Insect Sci. Applic. Vol. 19, No. 2/3, pp. 193-198, 1999 Printed in Kenya. All rights reserved 0191-9040/99 $3.00 + 0.00 © 1999 ICIPE EFFECT OF ORAL ADMINISTRATION OF SODIUM FLUORIDE ON FOOD AND WATER UTILISATION IN SILKWORM, BOMBYX MORI L. ...

Research paper thumbnail of Production of hydrocarbon compounds by endophytic fungi Gliocladium species grown on cellulose

Bioresource Technology, 2011

Endophytic fungi belonging to the genus Gliocladium are able to degrade plant cellulose and synth... more Endophytic fungi belonging to the genus Gliocladium are able to degrade plant cellulose and synthesize complex hydrocarbons under microaerophilic conditions. These fungi could thus be used to produce biofuels from cellulosics without the need for hydrolytic pretreatments. Gas chromatography-mass spectrometry-solid-phase micro-extraction (GC-MS-SPME) of head space gases from Gliocladium cultures demonstrated the production of C 6 -C 19 hydrocarbons including hexane, benzene, heptane, 3,4dimethyl hexane, 1-octene, m-xylene, 3-methyl nonane, dodecane, tridecane, hexadecane and nonadecane directly from the cellulosic biomass. Hydrocarbon production was 100-fold higher in co-cultures of Gliocladium and Escherichia coli than in pure Gliocladium cultures. The dry mycelia weight is stable at stationary period in co-culture condition which may lead to synthesize more hydrocarbons. These fungi could potentially be developed into cost-effective biocatalysts for production of biofuels.

Research paper thumbnail of Effect of culture medium composition on Trichoderma reesei’s morphology and cellulase production

Bioresource Technology, 2009

The objective of this study was to determine how fungal morphology influences the volumetric cell... more The objective of this study was to determine how fungal morphology influences the volumetric cellulase productivity of Trichoderma reesei cultured in four media with lactose and lactobionic acid as fed-batch in a 7 L stirred tank bioreactor. The use of a cellulose-yeast extract culture medium yielded the highest enzyme production with a volumetric enzyme activity of 69.8 U L À1 h À1 , and a maximum fungal biomass of 14.7 g L À1 . These findings were associated with the following morphological characteristics of the fungus: total mycelia was 98% of total mean projected area, mean hyphae length of 10 mm, mean hyphae volume of 45.1 mm 3 , mean hyphae diameter of 7.9 lm, number of branches 9, and number of tips per hypha 29. A positive correlation was found between the total mycelia, the number of tips and the volumetric enzyme productivity, indicating the weight of these variables on the enzyme productivity.

Research paper thumbnail of Culture-based strategies to enhance cellulase enzyme production from Trichoderma reesei RUT-C30 in bioreactor culture conditions

Biochemical Engineering Journal, 2008

Filamentous fungi Trichoderma reesei are considered to be one of the most efficient hyper produce... more Filamentous fungi Trichoderma reesei are considered to be one of the most efficient hyper producers of cellulase that is used in industry. Cellulase production by T. reesei was carried out using high concentration of cellulose to substitute glucose with the aim to improve cellulase production while trying to reduce production costs. The experiments were conducted separately as fed batch growth with T. reesei cultured using four media in a 7 L stirred tank bioreactor. A mixture of lactose and lactobionic acid was added into the bioreactor as cellulase inducers. The use of a cellulose-yeast extract culture medium yielded the highest enzyme and cell production with a volumetric enzyme activity of 69.8 U L −1 h −1 , a filter paper activity of 5.02 U mL −1 , a CMCase activity of 4.2 U mL −1 , and a fungal biomass of 14.7 g L −1 . The biomass concentration as a function of time was constant with relatively rapid, early growth on easily metabolized growth medium components (yeast extract), followed by a second slower growth phase due to hydrolysis of cellulose, which follow cellulase concentration augmentation. The costs to produce 1 L of production medium in laboratory-scale experiments were calculated to compare the tested media.

Research paper thumbnail of Effect of mechanical agitation on the production of cellulases by Trichoderma reesei RUT-C30 in a draft-tube airlift bioreactor

Biochemical Engineering Journal, 2010

With the aim to produce cellulases and to study the effect of mechanical agitation, a 35 L draft-... more With the aim to produce cellulases and to study the effect of mechanical agitation, a 35 L draft-tube airlift bioreactor equipped with a mechanical impeller was developed and validated to grow Trichoderma reesei RUT-C30 in a cellulose culture medium with lactose and lactobionic acid as fed batch. Cultures carried out without mechanical agitation resulted in higher volumetric enzyme productivity (200 U L −1 h −1 ), filter paper activity (17 U mL −1 ), carboxymethyl cellulase activity (11.8 U mL −1 ) and soluble proteins (3.2 mg mL −1 ) when compared to those with agitation. Stereo and polarized light microscopy analyses reveal that mechanical agitation resulted in shorter mycelial hyphae and larger numbers of tips. (P. Vermette). two zones: an upward and a downward flow zones. The zone where gases are sparged along with the riser (referred to as the upward flow zone) has a higher gas holdup than the relatively gas-free downward flow zone [7], generating the circulation loop pattern. Airlift bioreactors have been tested as fermenters in many biochemical processes, such as in wastewater treatment, animal cell cultures, and aerobic fermentations including the production of various enzymes, antibiotics, proteins, biomass and other products . In the absence of impellers, these reactors can be operated with no moving parts and bearings and therefore fewer seals, allowing extended aseptic operations. They have lower power consumption when compared to stirred tanks, good mixing capacity for media containing suspended solids, efficient mass and heat transfer and better defined flow patterns. Airlift bioreactors provide rapid mixing while retaining narrower shear stress distribution .

Research paper thumbnail of Enhanced enzyme production from mixed cultures of Trichoderma reesei RUT-C30 and Aspergillus niger LMA grown as fed batch in a stirred tank bioreactor

Biochemical Engineering Journal, 2008

For the complete hydrolysis of cellulose, the cellulolytic fungi produce a whole set of commercia... more For the complete hydrolysis of cellulose, the cellulolytic fungi produce a whole set of commercially important enzymes called cellulases. The aim of this work was to investigate an approach to enhance the production of these enzymes by co-culturing Trichoderma reesei and Aspergillus niger in a bioreactor to convert cellulose substrate into soluble sugars through a synergetic action of enzyme complex simultaneously produced by these two fungi. The experiments were conducted as fed batch growth on a Cellulose-Yeast extract medium. A mixture of lactose and lactobionic acid was added into the bioreactor as cellulase inducers. The results of mixed culture experiments exhibited a highly significant increase in the production of volumetric enzyme activity (98.4 U L −1 h −1 ), filter paper activity (7.1 U mL −1 ), carboxymethyl cellulase activity (4.7 U mL −1 ), soluble proteins (2.1 mg mL −1 ), dry biomass (21.4 g −1 L −1 ), and percentage of utilized cellulose (89.4%) as compared with A. niger monocultures.

Research paper thumbnail of Conjugation of laccase from the white rot fungus Trametes versicolor to chitosan and its utilization for the elimination of triclosan

Bioresource Technology, 2011

A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-eth... more A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) as the cross-linking agent. Laccase-chitosan conjugation strategies were tested using different molar ratios of glucosamine monomer/protein with different molar excess ratios of EDC relative to laccase. Immobilization techniques were developed to improve the stability against thermal and chemical denaturation, storage and reusability of this biocatalyst. The conjugation resulted in a solid biocatalyst with an apparent laccase activity of ±626 U/g, 12 and 60 folds higher in the conjugation efficiency of biocatalyst relative to the immobilized and free laccase activity respectively when compared with zero EDC/laccase ratio used in conjugation solution. The conjugated laccases formed successfully eliminated the emerging pollutant triclosan (TCS) from aqueous solutions, having a higher potential to transform TCS than free laccase. UPLC-QTOF results indicate the formation of TCS oligomers. Furthermore, they are the first evidence of direct dechlorination of TCS mediated by the oxidative action of laccases.

Research paper thumbnail of Embryonic development following microsurgical restoration of the diploid constitution in the human tripronuclear zygote

Fertility and Sterility, 2015

Research paper thumbnail of Conjugation of laccase from the white rot fungus Trametes versicolor to chitosan and its utilization for the elimination of triclosan

Bioresource Technology, 2011

A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-eth... more A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) as the cross-linking agent. Laccase-chitosan conjugation strategies were tested using different molar ratios of glucosamine monomer/protein with different molar excess ratios of EDC relative to laccase. Immobilization techniques were developed to improve the stability against thermal and chemical denaturation, storage and reusability of this biocatalyst. The conjugation resulted in a solid biocatalyst with an apparent laccase activity of ±626 U/g, 12 and 60 folds higher in the conjugation efficiency of biocatalyst relative to the immobilized and free laccase activity respectively when compared with zero EDC/laccase ratio used in conjugation solution. The conjugated laccases formed successfully eliminated the emerging pollutant triclosan (TCS) from aqueous solutions, having a higher potential to transform TCS than free laccase. UPLC-QTOF results indicate the formation of TCS oligomers. Furthermore, they are the first evidence of direct dechlorination of TCS mediated by the oxidative action of laccases.

Research paper thumbnail of Efficiency of food and dietary water utilisation and cocoon conversion in the new multivoltine breeds of silkworm, Bombyx mori L

Journal of Insect Science, 2002

Food and dietary water intake and their utilization in the new multivoltine breeds of silkworm Bo... more Food and dietary water intake and their utilization in the new multivoltine breeds of silkworm Bombyx marl L., viz. BL - 23, BL -24 and PM as control ted ad Ilbitum on M 5 mulberry leaf during 5th instar at the temperature of 26 ′ 1°C and 75 ′ 5% R.H. are reported. In the new multivoltine breeds, the larval duration was significantly shorter from 3.25 (BL - 23) to 3.50 (BL -24) days than the Pure Mysore race. The decrement in dry food consumed, food assimilated, assimilation efficiency, food oxidized, feeding rete, assimilation rate and metabolic rate was noticed in the new breeds when compared with the control. However, the conversion efficiencies (K 1 & K 2 ) and water retention efficiency were significantly higher in the new breeds. Due to higher conversion efficiencies, the larval biomass accumulation and cocoon conversion efficiencies were higher in the new breeds. The causative factors responsible for these changes have been discussed.

Research paper thumbnail of Facile Extraction of Wheat Straw by Deep Eutectic Solvent (DES) to Produce Lignin Nanoparticles

ACS Sustainable Chemistry & Engineering

A detailed investigation of choline chloride-lactic acid (ChCl-LA)-based deep eutectic solvent (D... more A detailed investigation of choline chloride-lactic acid (ChCl-LA)-based deep eutectic solvent (DES) extraction of lignin nanoparticles from herbaceous biomass (wheat straw) was conducted. It was found that DES can extract high purity lignin (up to 94.8%) with a high yield (up to 81.5% from air-dried samples and 85.9% from oven-dried samples) from wheat straw. The cleavages of ether bonds in lignin, as well as the linkages between lignin and hemicelluloses during DES treatments at different conditions, were analyzed. The effects of reaction time, treatment temperature and water content in wheat straw on lignin yield, purity, and chemical structure were determined. The water content in biomass was found to affect the hydrogen bond interaction between lignin and DES, which was a key factor influencing the lignin extraction yield and chemical properties of separated lignin. The lignin extracted from wheat straw by DES consists of well-dispersed nanoparticles with a narrow size distribution peaking at 70–90 nm. The mechanism of ChCl-LA-based DES depolymerization and extraction of lignin from wheat straw is discussed.

Research paper thumbnail of Kinetic understanding of nitrogen supply condition on biosynthesis of polyhydroxyalkanoate from benzoate by Pseudomonas putida KT2440

Bioresource Technology

Nitrogen supply is critical to the synthesis of intracellular PHA in various bacteria. However, t... more Nitrogen supply is critical to the synthesis of intracellular PHA in various bacteria. However, the specific role of the nitrogen in synthesizing PHA from benzoate, a lignin model compound use for the study of bacteria catabolism of aromatics, is still not clear. In this study, two culture conditions were maintained for Pseudomonas putida KT2440 to produce PHA using benzoate as a carbon source. Under nitrogen-limited and surplus conditions, the accumulation of PHA was to 37.3% and 0.25% of cell dry weight, respectively. A model fit to the kinetics of biomass growth and PHA accumulation showed good agreement with data. GC-MS and NMR showed that PHA contained six hydroxyl fatty acid monomers under nitrogen-limited conditions, while two monomers were identified under nitrogen surplus conditions. The average molecular weight of PHA increased after the nitrogen source was exhausted. These results provide a promising strategy for optimization of lignin to PHA yields.

Research paper thumbnail of Cocoon Yield Pattern and Analysis of Water, Soil and Leaves from Mulberry Gardens Irrigated with Polluted Water Around Bangalore, India

Sericulturists in the vicinity of Bangalore city irrigate their mulberry gardens with Vrishabhava... more Sericulturists in the vicinity of Bangalore city irrigate their mulberry gardens with Vrishabhavathy stream water, which is polluted with domestic and industrial wastes from the city. To investigate the effect of pollutants on silkworm crops, a detailed field survey was conducted to study the cocoon yield pattern of the crops raised on mulberry irrigated with wastewater as against irrigation by bore/open wells. The villages along the stream were grouped into five test batches at about a distance of km from each other. The seasonal yield data with relevant information were collected through questionnaires from 117 rearers using stream water and 35 rearers using bore/open wells, the latter serving as control group. The average yield for 100 layings was 46 to 57 kg in the control group whereas in test groups, it ranged between 34 to 51 kg in the first test group and 22 to 38 kg in the rest. The difference in yield was kg depending on the season between control and test batches. In summ...

Research paper thumbnail of 2015 - Ahring et al. - Making lignin accessible for anaerobic digestion by wet-explosion pretreatment

The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosi... more The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosion pretreatment promotes lignin solubility. 4.5 times higher methane yield observed as a result of the pretreatment. 44.4% lignin in pretreated material was actually converted in the AD process. Aliphatic compounds formed in the pretreatment were utilized by microbes.

Research paper thumbnail of Making lignin accessible for anaerobic digestion by wet-explosion pretreatment

Bioresource Technology, 2014

The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosi... more The pretreatment of feedlot manure was performed using 4 bars oxygen. Oxygen assisted wet-explosion pretreatment promotes lignin solubility. 4.5 times higher methane yield observed as a result of the pretreatment. 44.4% lignin in pretreated material was actually converted in the AD process. Aliphatic compounds formed in the pretreatment were utilized by microbes.

Research paper thumbnail of Production of hydrocarbons by Aspergillus carbonarius ITEM 5010

Fungal Biology, 2015

Lignocellulosic biomass a b s t r a c t

Research paper thumbnail of Culture-Based Strategies for Reduction of Protease Activity in Filtrates from Aspergillus niger NRRL-3

World Journal of Microbiology and Biotechnology, 2005

While Aspergillus strains are also being considered as potential hosts for production of extracel... more While Aspergillus strains are also being considered as potential hosts for production of extracellular heterologous proteins, the proteases produced by the host are highly problematic in that they typically modify and degrade the recombinant proteins. Culture-based approaches for minimization of protease activity in culture supernatants of Aspergillus niger NRRL-3 included reduction or elimination of peptide nitrogen in the medium, preferential use of a defined salts medium rather than a non-peptide nitrogen medium containing yeast-nitrogen base, supplementation of the medium with carboxymethylcellulose and cultivation at pH 6.5 rather than 7.5. In general, increased proteolytic activity was observed after maximum biomass was observed and biomass was declining suggesting the majority of protease activity was released by cell lysis. Carboxymethylcellulose shifted mycelial morphology from pelleted to filamentous. Mycelium lysis in the centre of pellets, with resultant release of intracellular proteases, would explain why filamentous cultures exhibited much lower proteolytic activity than pelleted cultures.

Research paper thumbnail of Incorporation of pepstatin into culture media for reduction of protease activity in filtrates from Aspergillus niger NRRL-3

Process Biochemistry, 2006

Aspergillus species have been used in different industrial applications including extracellular e... more Aspergillus species have been used in different industrial applications including extracellular enzyme production and as potential hosts for recombinant heterologous proteins production because of their excellent growth and fermentation properties. However, recombinant protein production levels are typically low due to the impact of Aspergillus proteases in modifying and degrading the heterologous proteins, especially in the extracellular medium. The potential of using the protease inhibitor pepstatin in filamentous Aspergillus niger culture was investigated in this study. The majority of protease activity was released into the medium as biomass content decreases after maximum biomass concentration was attained and a low concentration of pepstatin effectively inhibited the extracellular protease activity to an extent of 80-90%. The effectiveness of pepstatin in inhibiting the majority of protease activity was further demonstrated in media supplemented with both non-peptide and peptidecontaining nitrogen sources. Pepstatin addition had no effect on microbial growth. Dilution of the culture filtrate released inhibition, indicating that pepstatin did not have a notable effect on protease production and that inhibition was reversible. #

Research paper thumbnail of Chymostatin can combine with pepstatin to eliminate extracellular protease activity in cultures of Aspergillus niger NRRL-3

Journal of Industrial Microbiology & Biotechnology, 2007

Aspergillus strains are being considered as potential hosts for recombinant heterologous protein ... more Aspergillus strains are being considered as potential hosts for recombinant heterologous protein production because of their excellent extracellular enzyme production characteristics. However, Aspergillus proteases are problematic in that they modify and degrade the heterologous proteins in the extracellular medium. In previous studies we observed that media adjustments and maintenance of a filamentous morphology greatly reduced protease activity and that a low concentration of the aspartic protease inhibitor pepstatin inhibited the latter protease activity to the extent of approximately 90%. In this paper we report that when the serine protease inhibitor chymostatin is used in combination with pepstatin 99-100% of total protease activity in Aspergillus cultures is inhibited. In protease assays a concentration of 30 microM chymostatin combined with 0.075 microM pepstatin was required for maximum inhibition. Inhibitor concentrations of chymostatin and pepstatin of 120 and 0.3 microM, respectively, when added to Aspergillus cultures, has no significant effect on biomass production, glucose utilization or culture pH pattern. The potential of using these protease inhibitors in cultures of recombinant Aspergillus strains producing heterologous proteins will now be investigated to determine if the previously observed recombinant protein denaturing effects of Aspergillus proteases can be negated.

Research paper thumbnail of Effect of Oral Administration of Sodium Fluoride on Food and Water Utilisation in Silkworm, Bombyx mori L

International Journal of Tropical Insect Science, 1999

Page 1. Insect Sci. Applic. Vol. 19, No. 2/3, pp. 193-198, 1999 Printed in Kenya. All rights rese... more Page 1. Insect Sci. Applic. Vol. 19, No. 2/3, pp. 193-198, 1999 Printed in Kenya. All rights reserved 0191-9040/99 $3.00 + 0.00 © 1999 ICIPE EFFECT OF ORAL ADMINISTRATION OF SODIUM FLUORIDE ON FOOD AND WATER UTILISATION IN SILKWORM, BOMBYX MORI L. ...

Research paper thumbnail of Production of hydrocarbon compounds by endophytic fungi Gliocladium species grown on cellulose

Bioresource Technology, 2011

Endophytic fungi belonging to the genus Gliocladium are able to degrade plant cellulose and synth... more Endophytic fungi belonging to the genus Gliocladium are able to degrade plant cellulose and synthesize complex hydrocarbons under microaerophilic conditions. These fungi could thus be used to produce biofuels from cellulosics without the need for hydrolytic pretreatments. Gas chromatography-mass spectrometry-solid-phase micro-extraction (GC-MS-SPME) of head space gases from Gliocladium cultures demonstrated the production of C 6 -C 19 hydrocarbons including hexane, benzene, heptane, 3,4dimethyl hexane, 1-octene, m-xylene, 3-methyl nonane, dodecane, tridecane, hexadecane and nonadecane directly from the cellulosic biomass. Hydrocarbon production was 100-fold higher in co-cultures of Gliocladium and Escherichia coli than in pure Gliocladium cultures. The dry mycelia weight is stable at stationary period in co-culture condition which may lead to synthesize more hydrocarbons. These fungi could potentially be developed into cost-effective biocatalysts for production of biofuels.

Research paper thumbnail of Effect of culture medium composition on Trichoderma reesei’s morphology and cellulase production

Bioresource Technology, 2009

The objective of this study was to determine how fungal morphology influences the volumetric cell... more The objective of this study was to determine how fungal morphology influences the volumetric cellulase productivity of Trichoderma reesei cultured in four media with lactose and lactobionic acid as fed-batch in a 7 L stirred tank bioreactor. The use of a cellulose-yeast extract culture medium yielded the highest enzyme production with a volumetric enzyme activity of 69.8 U L À1 h À1 , and a maximum fungal biomass of 14.7 g L À1 . These findings were associated with the following morphological characteristics of the fungus: total mycelia was 98% of total mean projected area, mean hyphae length of 10 mm, mean hyphae volume of 45.1 mm 3 , mean hyphae diameter of 7.9 lm, number of branches 9, and number of tips per hypha 29. A positive correlation was found between the total mycelia, the number of tips and the volumetric enzyme productivity, indicating the weight of these variables on the enzyme productivity.

Research paper thumbnail of Culture-based strategies to enhance cellulase enzyme production from Trichoderma reesei RUT-C30 in bioreactor culture conditions

Biochemical Engineering Journal, 2008

Filamentous fungi Trichoderma reesei are considered to be one of the most efficient hyper produce... more Filamentous fungi Trichoderma reesei are considered to be one of the most efficient hyper producers of cellulase that is used in industry. Cellulase production by T. reesei was carried out using high concentration of cellulose to substitute glucose with the aim to improve cellulase production while trying to reduce production costs. The experiments were conducted separately as fed batch growth with T. reesei cultured using four media in a 7 L stirred tank bioreactor. A mixture of lactose and lactobionic acid was added into the bioreactor as cellulase inducers. The use of a cellulose-yeast extract culture medium yielded the highest enzyme and cell production with a volumetric enzyme activity of 69.8 U L −1 h −1 , a filter paper activity of 5.02 U mL −1 , a CMCase activity of 4.2 U mL −1 , and a fungal biomass of 14.7 g L −1 . The biomass concentration as a function of time was constant with relatively rapid, early growth on easily metabolized growth medium components (yeast extract), followed by a second slower growth phase due to hydrolysis of cellulose, which follow cellulase concentration augmentation. The costs to produce 1 L of production medium in laboratory-scale experiments were calculated to compare the tested media.

Research paper thumbnail of Effect of mechanical agitation on the production of cellulases by Trichoderma reesei RUT-C30 in a draft-tube airlift bioreactor

Biochemical Engineering Journal, 2010

With the aim to produce cellulases and to study the effect of mechanical agitation, a 35 L draft-... more With the aim to produce cellulases and to study the effect of mechanical agitation, a 35 L draft-tube airlift bioreactor equipped with a mechanical impeller was developed and validated to grow Trichoderma reesei RUT-C30 in a cellulose culture medium with lactose and lactobionic acid as fed batch. Cultures carried out without mechanical agitation resulted in higher volumetric enzyme productivity (200 U L −1 h −1 ), filter paper activity (17 U mL −1 ), carboxymethyl cellulase activity (11.8 U mL −1 ) and soluble proteins (3.2 mg mL −1 ) when compared to those with agitation. Stereo and polarized light microscopy analyses reveal that mechanical agitation resulted in shorter mycelial hyphae and larger numbers of tips. (P. Vermette). two zones: an upward and a downward flow zones. The zone where gases are sparged along with the riser (referred to as the upward flow zone) has a higher gas holdup than the relatively gas-free downward flow zone [7], generating the circulation loop pattern. Airlift bioreactors have been tested as fermenters in many biochemical processes, such as in wastewater treatment, animal cell cultures, and aerobic fermentations including the production of various enzymes, antibiotics, proteins, biomass and other products . In the absence of impellers, these reactors can be operated with no moving parts and bearings and therefore fewer seals, allowing extended aseptic operations. They have lower power consumption when compared to stirred tanks, good mixing capacity for media containing suspended solids, efficient mass and heat transfer and better defined flow patterns. Airlift bioreactors provide rapid mixing while retaining narrower shear stress distribution .

Research paper thumbnail of Enhanced enzyme production from mixed cultures of Trichoderma reesei RUT-C30 and Aspergillus niger LMA grown as fed batch in a stirred tank bioreactor

Biochemical Engineering Journal, 2008

For the complete hydrolysis of cellulose, the cellulolytic fungi produce a whole set of commercia... more For the complete hydrolysis of cellulose, the cellulolytic fungi produce a whole set of commercially important enzymes called cellulases. The aim of this work was to investigate an approach to enhance the production of these enzymes by co-culturing Trichoderma reesei and Aspergillus niger in a bioreactor to convert cellulose substrate into soluble sugars through a synergetic action of enzyme complex simultaneously produced by these two fungi. The experiments were conducted as fed batch growth on a Cellulose-Yeast extract medium. A mixture of lactose and lactobionic acid was added into the bioreactor as cellulase inducers. The results of mixed culture experiments exhibited a highly significant increase in the production of volumetric enzyme activity (98.4 U L −1 h −1 ), filter paper activity (7.1 U mL −1 ), carboxymethyl cellulase activity (4.7 U mL −1 ), soluble proteins (2.1 mg mL −1 ), dry biomass (21.4 g −1 L −1 ), and percentage of utilized cellulose (89.4%) as compared with A. niger monocultures.

Research paper thumbnail of Conjugation of laccase from the white rot fungus Trametes versicolor to chitosan and its utilization for the elimination of triclosan

Bioresource Technology, 2011

A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-eth... more A commercial laccase from Trametes versicolor was conjugated with biopolymer chitosan using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) as the cross-linking agent. Laccase-chitosan conjugation strategies were tested using different molar ratios of glucosamine monomer/protein with different molar excess ratios of EDC relative to laccase. Immobilization techniques were developed to improve the stability against thermal and chemical denaturation, storage and reusability of this biocatalyst. The conjugation resulted in a solid biocatalyst with an apparent laccase activity of ±626 U/g, 12 and 60 folds higher in the conjugation efficiency of biocatalyst relative to the immobilized and free laccase activity respectively when compared with zero EDC/laccase ratio used in conjugation solution. The conjugated laccases formed successfully eliminated the emerging pollutant triclosan (TCS) from aqueous solutions, having a higher potential to transform TCS than free laccase. UPLC-QTOF results indicate the formation of TCS oligomers. Furthermore, they are the first evidence of direct dechlorination of TCS mediated by the oxidative action of laccases.