Ahmed Mohy El-Din | Agricultural Research Center (Egypt) (original) (raw)

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Papers by Ahmed Mohy El-Din

Chitinolytic bacterial candidate was isolated from mature compost and purified. The isolate was i... more Chitinolytic bacterial candidate was isolated from mature compost and purified. The isolate was identified as Streptomyces nigrifaciens. Optimization of growth conditions ( peptone N source, 45°C, pH 9, fermentor agitation speed 300 rpm, air flow rate 1L/min, 48 hours ) to obtain the highest chitinolytic activity under lab scale led to increment of chitinase production expressed as chitinolytic activity from 58.816 U/ml up to 2129 U/ml (36 times). Chitinase production in fermentor was achieved on local chitinic wastes and the resulting crude enzyme was subjected to partial purification steps (ammonium sulphate precipitation and chitin affinity), the resulting semi purified chitinolytic fractions were separated. Three partially purified chitinases were separated from the SUP named S1, S2 and S3 of 1414.7 U/mg, 616.4 U/mg and 641.3 U/mg activities, respectively. From the chitinic debris, two partially purified chitinases having high affinity to chitin were separated and named P1 and P2 of 748.6 U/mg and 5344.3 U/mg activities, respectively. The optimization of temperature revealed the superiority of P2 fraction, as the chitinolytic specific activity increased from 3070.700 U/mg at 37°C to 9126.421 U/mg of P2 at 45°C raising the purification fold to 2.97 and its yield reached 4%. The P2 optimum pH and substrate concentration for hydrolyzing colloidal chitin were found to be 10 and 22 mg/ml, respectively.

Twenty eight pre-identified fungal isolates and strains were tested qualitatively for their cellu... more Twenty eight pre-identified fungal isolates and strains were tested qualitatively for their cellulolytic activities, among which 12 superior producers were quantitatively tested. Three Aspergillus spp. namely A5, A6 and A7 were found to be the best cellulolytic fungi, while both Aspergillus terreus NRRL260 and Phanerochaete chrysosporium NRRL6361 were found to be the best xylanase producers. On solid state fermentation (SSF) using pretreated rice straw (RS), the Aspergillus spp. A5, A6 and A7 gave total cellulases (as FPase), exo-cellulases (as CMCase) and cellobiase (as β-glucosidase) activities of ≥ 16, 130 and 21U.g-1 ds, respectively. On the other hand, Aspergillus terreus NRRL260 showed maximum xylanases activity of 804 U.g-1 ds. The recovered crude enzymes forming the crude enzyme mixture (CEM) was concentrated (LCEM), ammonium sulfate fractionated (PPE1), were semi-purified by gel permeation on Sephadex G100 and finally lyophilized to powder form (PPE2). The resulting cellulases specific activities were 0.50, 0.68, 1.01 and 1.47 U.mg-1 , respectively. Those purification and concentration steps resulted in purification fold increase by 1.28, 2.08 and 2.78 for LCEM, PPE1 and PPE2, respectively. PPE2 achieved maximum degree of saccharification (DoS) at enzyme load ≥ 10 FPU, substrate concentration ≥ 5% and incubation period after 48 hr to be 85%, 87% and 88%, respectively.

Nine fungal strains known for their cellulolytic activities including: Aspergillus oryzae, Asperg... more Nine fungal strains known for their cellulolytic activities including: Aspergillus oryzae, Aspergillus versicolor-I, Aspergillus versicolor-II, Fusarium oxysporum, Fusarium oxysporum-I, Mucor indicus, Penicillium citrinum, Phanerochaete chrysosporium and Pleurotus sp., were tested for their fermentation capabilities on Mandels medium supplied with 10% fructose as sole carbon source at 35°C under minor air conditions. Among the nine strains F. oxysporum recorded the best ethanol production to be 0.077g ethanol / g carbon. Mandels medium components were further modified individually for best ethanol production. Throughout nutritional development the ethanol yield efficiency increased from 15 up to 44%, using yeast extract as sole nitrogen source at C:N ratio of 2:1 and initial pH=5. Fructose was tested at concentrations of 5%, 10%, and 15%, altered ratio between fructose consumed in ethanol production and that in fungal growth to be 2.2:1, 1.1:1 and 1:1.8, respectively, of which 5% fructose was considered the best in spite of 10% fructose that gave fermentation yield efficiency of 44.9%.

This study was conducted to test nine cellulytic filamentous fungi including: Aspergillus oryzae,... more This study was conducted to test nine cellulytic filamentous fungi including: Aspergillus oryzae, Aspergillus versicolor-I, Aspergillus versicolor-II, Fusarium oxysporum, Fusarium oxysporum-I, Mucor indicus, Penicillium citrinum, Phanerochaete chrysosporium and Pleurotus sp., to ferment glucose. They were tested on Mandels medium during 14 days of incubation at 35°C under minor air conditions. The best ethanol producers were F. oxysporum, Ph. chrysosporium and F. oxysporum-I, recording 0.464, 0.360 and 0.325g ethanol/g carbon. Modifications to Mandels medium were done individually to magnify ethanol production and deselect aside lower ethanol producers. Nitrogen sources substitution including ammonium sulfate, ammonium phosphate, casein, peptone, potassium nitrate and yeast extract was done. Different C:N ratios (2:1, 4:1, 6:1 and 8:1) and pH levels (4, 5 and 6) were tested. Glucose concentrations including 100, 200 and 300g/L were also tested. Ph. chrysosporium was selected for its best production recording 0.847 g ethanol/g carbon corresponding to 33.9 g/L, utilizing yeast extract as N source, at C:N ratio of 2:1, pH=5 and initial glucose level of 100g/L. The ethanol yield was improved 2.4 times (from 14% to 33.9%). However, either pH=4 or 300g/L glucose was repressor for ethanol production.

Rice straw (RS) and sugarcane bagasse (SCB) were subjected individually to four different distinc... more Rice straw (RS) and sugarcane bagasse (SCB) were subjected individually to four different distinct pretreatments: conventional alkaline (2% NaOH, 85°C for 1h), alkaline (1.5% NaOH) / H2O2, alkaline (1.5% NaOH) / NaClO and mild alkaline (1% NaOH) for 24h at room temperature. Efficiency of each pretreatment was evaluated through their effect on each lignocellulosic biomass structure as well as their susceptibility to enzymatic hydrolysis via commercial cellulases derived from Tichoderma reesei ATCC 26921. Approximately, one-half of lignin and most of hemicellulose present in both Rs and SCB were solubilized by alkaline/oxidative pretreatment at room temperature for 24h. Relative cellulose content of the pretreated samples was increased (>35%) accompanied with a decrease in crystallinity index (>2.5 times). Consequently, promotion of cellulose content and demotion of hemicellulose and lignin content facilitated the enzymatic hydrolysis (10 FPU.g-1, pH 4.8, 50°C for 24h) of treated substrate (2.5%), as it increased reducing sugars production (671.2 and 750 mg.g-1) and saccharification yield (81.54 and 87.35%) for RS and SCB, respectively. The alkaline/hypochlorite pretreatment is the most efficient method among the four tested ones.

A chemically defined medium was developed to support the growth of domestic isolate of Rhizobium ... more A chemically defined medium was developed to support the growth of domestic isolate of Rhizobium radiobacter (HQ 395610-Egypt) and its production of agrocin. Various supplements were investigated for their effect on production of agrocin 84 using the method of well-diffusion assay against Agrobacterium tumefaciens. D-fructose as carbon source was found to be a better substrate for agrocin production compared to the other sugars and sugar alcohols tested, while monobasic ammonium phosphate was the best nitrogen source than other organic and inorganic ones. On the other hand, scaling up C/N ratio to 1:16 under pH 5.5 at 35˚C incubation temperature maximized the production after 12 hr. In the fermentor, scaling up to 1L maximized the results nearly twice at agitation speed of 200 rpm and airflow of 1 Lpm. Agrocin fragments were successfully separated, partially purified and well located by UV spectrum at 254 nm.

Response variation for salt tolerance was assessed in two Zea mays L. cultivars; Giza 2 (salt tol... more Response variation for salt tolerance was assessed in two Zea mays L. cultivars; Giza 2 (salt tolerant) and Hybrid triple 314 (salt sensitive) amended in presence of Rhizobium radiobacter strain (HQ 395610-Egypt) under two N fertilization regimes (75% and 100%). Soil samples tested for enzymatic activities revealed that R. radiobacter inoculation increased nitrogenase and hydrolases activities particularly after 90 and 45 days. The leaf sample analyzed for inorganic osmolytes (potassium and sodium) showed that both cultivars had high K/Na ratio when treated with R. radiobacter, while total chlorophyll, soluble sugars and peroxidase activity increased. Proline stress-response was also reduced by R. radiobacter inoculation. Substantial variations were observed in the grain quality and yield for both cultivars due to the different treatments. The grain yield increased by 71% in cv. Giza and 48% in cv. Hybrid when R. radiobacter treatment was combined with full N fertilization level. [Lobna A. Moussa, Mohy E.A. and El Banna Ib.M. Zea Mays Cultivar Behavior as Affected by Rhizobium Radiobacter Inoculation in Salt-Stressed Environments. J Am Sci 2012; 8(7):743-750]. (ISSN: 1545-1003). http://www.americanscience.org.109