Saccharification of Leptochloa fusca (kallar grass straw) using thermostable cellulases (original) (raw)
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High-performance hydrolysis of wheat straw using cellulase and thermomechanical pretreatment
Process Biochemistry, 2011
Wheat straw was ground and pretreated with a thermomechanical process before exposure to a mixture of cellulases (Celluclast). The thermomechanical process known as DIC (Détente Instantanée Contrôlée), which is similar to the steam explosion process, was used to pretreat the lignocellulosic biomass through a flash expansion. The results demonstrate that crushing the wheat straw increased the hydrolysis yields. The initial hydrolysis rates and the final yields of hydrolysis increased relative to those of the untreated straw as a result of the DIC pretreatment. After optimization, the hydrolysis process resulted in a glucose yield of 31 g/100 g of straw, which corresponds to approximately 90% of the theoretical cellulose value. A fermentation procedure was performed using the microorganism Saccharomyces cerevisiae, and the results confirmed the production of bioethanol (11.5 g/100 g of pretreated straw). The adsorption isotherms of cellulases on wheat straw and the enzyme kinetics of hydrolysis of the wheat straw were also studied using different concentrations of Celluclast. The kinetic parameters (maximal velocity, V emax , and half-saturation constant, K e) were determined from the initial velocities. K ad (adsorption coefficient) results show that the DIC pretreatment of the straw decreased K ad six-fold compared to that of the untreated straw (15.54 vs 2.52 g of enzymes/g of biomass, respectively), confirming that the DIC pretreatment produced a substrate that is more accessible to cellulases.
Environmental Progress & Sustainable Energy, 2015
The cost effective production of cellulolytic enzymes and their use for generating higher reducing sugars from lignocellulosic biomass is critical for attaining the commercial viability of lignocellulosic biofuels production. Optimizing the use of locally available agroresidues and natural nutritional alternatives for fungal growth and enzyme production can reduce the cost of enzyme production. In the present work, maximum cellulolytic activity of 30.85 IU/gds was obtained from Trichoderma reesei NCIM 1186 using wheat bran as the substrate and coconut water as the nutritional supplement. The produced cellualse was used for enzymatic saccharification of phosphoric acid pretreated wheat straw. The enzymatic sachharification was optimized through central composite design (CCD) based response surface methodology (RSM). Maximum reducing sugar yields of 371.44 mg/ g dry substrate were obtained at 18% (w/v) substrate concentration, 50 C and 24 h of incubation time. Further, the saccharified sugar hydrolysate was fermented using S. cerevisiae NCIM 3215. Maximum ethanol production (2.58% w/v) obtained after 24 h of fermentation at 30 C.
Enzyme and Microbial Technology, 2003
The production of cellulose and hemicellulose-degrading enzymes by cultivation of Aspergillus niger ATCC 9029, Botrytis cinerea ATCC 28466, Penicillium brasilianum IBT 20888, Schizophyllum commune ATCC 38548, and Trichoderma reesei Rut-C30 was studied. Wet-oxidised wheat straw suspension supplemented with NH 4 NO 3 , MgSO 4 , and KH 2 PO 4 was used as cultivation medium aiming to obtain an enzyme mixture optimal for enzymatic hydrolysis of wet-oxidised wheat straw. The cultivations with B. cinerea and P. brasilianum gave the highest endoglucanase (EC 3.2.1.4) and -glucosidase (EC 3.2.1.21) activities, in contrast to the other fungi where lower activities were found. The culture filtrates were concentrated by ammonium sulphate precipitation. After enzyme concentration, the highest enzyme activities (1.34 FPU/ml) were found in the culture broth originating from P. brasilianum. Enzymatic hydrolysis of filter cake from wet-oxidised wheat straw for 48 h with an enzyme loading of 5 FPU/g biomass resulted in glucose yields from cellulose of 58% (w/w) and 39% (w/w) using enzymes produced by P. brasilianum and a commercial enzyme mixture, respectively. At higher enzyme loading (25 FPU/g biomass) using either enzyme mixtures the glucose yield from cellulose was in the range of 77-79% (w/w).
Practical use of the polysaccharidic fraction of lignocellulosic material is limi- ted by its high lignin content. In this study the lignin-degrading white-rot fungus Trametes trogii Berk. in Trog. was used in the solid-state pre-treatment of wheat straw and the effi- ciency of the enzymatic hydrolysis of the residual cellulose after pre-treatment was analy- sed. Glucose, mineral nitrogen and yeast extract were used to supplement the pre-treatment minimal medium. Results were determined on the basis of levels of glucose and total redu- cing sugars released after batch incubation with foreign cellulases. The principal effect of medium components, as well as the effects of their interaction, were investigated using a two-level full factorial analysis in function of pre-treatment and hydrolysis times. Eviden- ce is provided to show that better results are obtained in the presence of glucose, while the presence of nitrogen sources results in lower yields irrespective of the time course ...
A white rot fungus, identified as Trametes hirsuta based on morphological and phylogenetic analysis, was found to contain efficient cellulose degrading enzymes. The strain showed maximum endoglucanase (EG), cellobiohydrolase (CBH) and ß-glucosidase (BGL) activities of 55, 0.28 and 5.0 U/mg-protein, respectively. Rice straw was found to be a potentially good substrate for growth of T. hirsuta for cellulase production. Statistical experimental design was used to optimize hydrolysis parameters such as pH, temperature, and concentrations of substrates and enzymes to achieve the highest saccharification yield. Enzyme concentration was identified as the limiting factor for saccharification of rice straw. A maximum saccharification rate of 88% was obtained at an enzyme concentration of 37.5 FPU/g-substrate after optimization of the hydrolysis parameters. The results of a confirmation experiment under the optimum conditions agreed well with model predictions. T. hirsuta may be a good choice for the production of reducing sugars from cellulosic biomass.
Enzymatic Saccharification of Pretreated Wheat Straw byT. ReeseiCellulases andA. Nigerβ-Glucosidase
Biocatalysis and Biotransformation, 2000
h i g h l i g h t s Solids-recycling at steady state was compared to sequential and batch hydrolysis. Volumetric productivity was increased by solids-recycling and sequential hydrolysis. Solids-recycling is a method for product removal rather than enzyme recycling. Solids-recycling requires less unit operations than sequential hydrolysis. A solids-recycle process was modeled, based on a geometrical series.
Journal of Chemical Technology & Biotechnology, 2013
BACKGROUND: Advances on enzyme technology have improved the economics of cellulosic ethanol. Nevertheless, there is still great interest to improve the production and the characteristics of the enzymatic preparations. One possibility to reduce the cost of the enzymes is on-site enzyme production in a biorefinery plant, in which part of the lignocellulosic material already available can be used as a cheap carbon source in the enzyme production. RESULTS: Steam exploded wheat straw at two different severity conditions was evaluated as carbon source for enzyme production by Trichoderma reesei. The results showed that volumetric production of cellulases and β-glucosidase increased when using a carbon source with high cellulose content. When a carbon source with a higher content of hemicellulose was used the enzymatic mixture showed significantly higher proportions of hemicellulase activities (xylanase, β-xylosidase and α-L-arabinofuranosidase), which had a positive effect on subsequent enzymatic hydrolysis. CONCLUSIONS: The proportion of cellulose and hemicellulose in the carbon source has an influence on the composition of the enzymatic cocktail. The higher the cellulose and hemicellulose content, the higher the titer of cellulase and hemicellulase produced by the fungus, respectively. The enzyme preparations with higher hemicellulase activities were more efficient in hydrolyzing xylan-containing substrates.
Enhanced cellulase production from Trichoderma reesei QM 9414 on physically treated wheat straw
Applied Microbiology and Biotechnology, 1986
Trichoderma reesei QM 9414 was grown on wheat straw as the sole carbon source. The straw was pretreated by physical and chemical methods. The particle size of straw was less than 0.177 mm. Growth of T. reesei QM 9414 was maximal with alkali-pretreated straw whereas cellulase production was optimal when physically pretreated straw was used as substrate. Cellulase yields expressed as IU enzyme activity/g cellulose present in the cultures were considerably higher when alkali pretreatment of wheat straw was omitted. Cellulase yields of 666 IU/g cellulose for filter paper activity (FPA) are the highest described for cultures of T. reesei QM 9414 carried out in analogous conditions. Crystallinity index of the cellulose contained in wheat straw increased slightly after alkali pretreatment. This increase did not decrease cellulose accessibility to the fungus. Delignification of wheat straw was not necessary to achieve the best cellulase production.
2015
A B S T R A C T Cellulases are a group of hydrolytic enzymes and are capable of degrading lignocellulosic materials. Cellulases have wide range of applications. This work focuses on factors relevant for improvement of enzymatic hydrolysis of rice straw by using isolated fungal strain from compost pit. Different cultural conditions were examined to assess their effect in optimizing enzyme production as well as for characterization of enzyme after partial purification. In comparison with WR (White rot fungi), our isolated strain 2b reports higher production of cellulases. K e y w o r d s Fungal cellulase, Lignocellulolytic agrowaste, Enzymatic saccharification
TJPRC, 2013
The cellulase production in solid state fermentation (SSF) by Trichoderma viride was investigated using wheat straw and papyrus straw as the substrate. Present study described the optimization of process parameters for the production of cellulases. The fermentation experiments were carried out in shake flasks using pretreated wheat straw and papyrus straw. Maximum production of cellulases from wheat straw (CMCase 1.62 U/ml/min) and from papyrus straw (PAPase 0.81 U/ml/min) was observed after a fermentation period of 70hrs at an incubation temperature of 30ºC. Initial pH of the culture medium was also optimized and a pH of 5.5 was found to support maximum growth and enzyme production. Different inorganic nitrogen sources were evaluated for the production of cellulases and ammonium sulphate was found to be the best. The enzyme production was further enhanced by carrying out fermentation experiments using 25 ml of culture medium in 250 ml flask inoculated with 4% inoculum.