M. Y. Kamat

Production of Aspergillus xylanase by lignocellulosic waste fermentation and its application

Strains of Aspergillus terreus and A. niger, known to produce xylanase with undetectable amounts of cellulase, were studied for xylanase (EC 3.2.1.8) production on various lignocellulosic substrates using solid state fermentation. Of the lignocellulosic substrates used, wheat bran was the best for xylanase production. The effects of various parameters, such as moistening agent, level of initial moisture content, temperature of incubation, inoculum size and incubation time, on xylanase production were studied. The best medium for A. terreus was wheat bran moistened with 1:5 Mandels and Strenberg mineral solution containing 0·1% tryptone, at 35 °C, and at inoculum concentration 2×107−2×108 spores 5 g−1 substrate; forA. niger, the best medium was wheat bran moistened with 1:5 Mandels and Strenberg mineral solution containing 0·1% yeast extract, at 35 °C, and at an inoculum concentration of 2×107−2×108 spores 5 g−1 substrate. Under these conditions, A. terreus produced 68·9 IU ml−1 of xylanase, and A. niger, 74·5 IU ml−1, after 4 d of incubation. A crude culture filtrate of the two Aspergillus strains was used for the hydrolysis of various lignocellulosic materials. Xylanase preparations from the two strains selectively removed the hemicellulose fraction from all lignocellulosic materials tested.

Gymnema sylvestre: A Memoir

Gymnema sylvestre is regarded as one of the plants with potent anti diabetic properties. This plant is also used for controlling obesity in the form of Gymnema tea. The active compound of the plant is a group of acids termed as gymnemic acids. It has been observed that there could be a possible link between obesity, Gymnemic acids and diabetes. This review will try to put forth an overall idea about the plant as well as present a molecular perspective linking the common medicine to the most common metabolic disorders.

Preparation, characterization and application of Aspergillus sp. xylanase immobilized on Eudragit S-100

Aspergillus sp. 5 (strain 5) and Aspergillus sp. 44 (strain 44) produced xylanase (34.3 and 32.7 IU ml-1, respectively) with very low levels of cellulases when grown on 1% wheat bran medium. Xylanase was non-covalently immobilized on Eudragit S-100 for saccharification. The system retained 70 and 80% of strain 5 and strain 44 xylanase activity, respectively. On immobilization, optimum temperature of activity broadened between 50 and 60 degrees C as compared to 50 degrees C in the case of the free enzymes. No significant shift in the pH optima was observed on immobilization. However, immobilization increased enzyme stability mainly by decreasing the temperature sensitivity to the inactivation reaction. The K(m) values increased from 5.6 to 8.3 mg ml-1 for strain 5 xylanase and 7.0 to 9.0 mg ml-1 for strain 44 xylanase. Enzymatic saccharification of xylan and wheat bran was improved on xylanase immobilization. Immobilized xylanase from both the strains produced three times more sugar as compared to free xylanase. In repeated batch saccharification studies immobilized xylanase was recycled three times without loss of enzyme activity.

Expanded bed affinity purification of bacterial α-amylase and cellulase on composite substrate analogue–cellulose matrices

Abstract Expanded bed purification of α-amylase and cellulase directly from unclarified fermentation broth was carried out on specially prepared composite affinity matrices. The concept used was incorporation of polymeric substrates/substrate analogue during cross-linking of cellulose to prepare rigid, porous, cross-linked composite affinity matrices for target enzymes. Of the several polymeric substrates/substrate-analogue used, alginic acid (AA) and microcrystalline cellulose (MCC) when used to prepare cross-linked composite matrices with cellulose, resulted in best affinity purification matrices for α-amylase and cellulase, respectively. These matrices were suitable for purification of the enzymes by batch, packed bed as well as expanded bed purification protocols. The optimized expanded bed protocol for α-amylase from Bacillus spp. B3 gave 51-fold purification on AA-CELBEADS with 69% recovery, whereas, cellulase from Bacillus spp. B21 was purified on MCC-CELBEADS to 18-fold purification with 97% recovery. The SDS-PAGE of both purified preparations showed single bands indicating significant purification on composite affinity adsorbents in a single step strategy.

Low-dose irradiation as a measure to improve microbial quality of ice cream

The present study was undertaken to investigate the efficacy of low-dose irradiation to improve the microbial safety of ice cream. Initially three different flavors (vanilla, strawberry and chocolate) of ice cream were exposed, at -72 degrees C, to doses of 1, 2, 5, 10 and 30 kGy to gamma-radiation. Irradiation at 1 kGy resulted in reduction of microbial population by one log cycle, thus meeting the requirement limits prescribed by Bureau of Indian Standards. Pathogens such as Listeria monocytogenes 036, Yersinia enterocoliticta 5692 and Escherichia coli O157:H19, respectively, showed the D10 values 0.38, 0.15 and 0.2 kGy in ice cream at -72 degrees C suggesting the efficacy of low doses (1 kGy) in eliminating them. Sensory evaluation studies of ice cream irradiated at 1, 2, 3 and 5 kGy by a 15 member panel demonstrated that doses higher than 2 kGy irradiation induced off-odour and an aftertaste was evident in vanilla ice cream. A radiation dose of 1 kGy was sufficient to eliminate the natural number of pathogens present in the ice cream. No statistically significant differences were observed in the sensory attributes of all the three flavours of ice cream either unirradiated or exposed to 1 kGy (P < 0.05).

Purification of Aspergillus sp xylanase by precipitation with an anionic polymer Eudragit S100

The separation of xylanases from the crude culture filtrates of Aspergillus sp 5 and Aspergillus sp 44 was carried out using affinity precipitation with a commercially available enteric polymer Eudragit S100. With affinity precipitation the yield of enzyme was 85.3, 82.7% with 10.8, 4.08-folds (specific activity of ammonium sulphate precipitate was taken as 100%) increases in the specific activity of Aspergillus sp 5 and Aspergillus sp 44, respectively. A comparison of SDS-PAGE electrophoretic patterns of the ammonium sulphate and purified enzyme by affinity precipitation showed significant purification of the enzyme. Zymogram analysis revealed recovery of three and two forms of xylanases from Aspergillus sp 5 and Aspergillus sp 44, respectively.

Immobilization of Aspergillus sp. on nylon bolting cloth for production of xylanase

Abstract Aspergillus sp. 5 and Aspergillus sp. 44, isolated from compost manure, were immobilized on a 400-mesh nylon bolting cloth. In shake flasks under a given set of conditions, the immobilization resulted in an absolutely clear residual broth, when compared with that containing freely suspended cells confirming complete adherence of the cells. It was found that this method of immobilization was simple and had no detrimental effects on the growth or activity of the cells. The enzyme productivity of immobilized Aspergillus sp. 5 was 1.68-fold higher than that of freely suspended cells, while for the case of Aspergillus sp. 44 the difference in productivity between freely suspended and immobilized cells was not significant. In repeated batch fermentation of both immobilized Aspergillus sp. 5 and Aspergillus sp. 44, the same biocatalyst yielded 103.93%, 97.02%, 51.8% and 97.52%, 72.08% xylanase activity in consecutive cycles.

Studies in polysaccharide production and growth of Azotobacter vinelandii MTCC 2459, a plant rhizosphere isolate

Azotobacter vinelandii MTCC 2459, a novel exopolysaccharide (EPS) producer, was isolated from Nelumbium nelumbo (lotus) stem. The EPS produced has a sugar composition different from the existing industrial gums (glucose, galactose and rhamnose). Optimization of the basal medium composition and other physical parameters (viz. pH, temperature, time, etc.) are reported in this paper. A final yield of 16·5% of the amount of the carbon source supplied was obtained in shake flask cultures, indicating the potential of the organism for production of useful EPS on a large (industrial) scale.

Production and optimization of certain growth parameters for an exopolysaccharide from Azotobacter vinelandii MTCC 2460 isolated from a plant rhizosphere

Azotobacter vinelandii MTCC 2460, a novel exopolysaccharide (EPS) producer, was isolated from Nelumbium nelumbo (lotus) stem. The EPS produced has a sugar composition different from that of existing industrial gums. Optimization of the basal medium composition and other physical parameters viz. pH, temperature and time has been reported in this paper. A final yield of 30% of the amount of carbon source i.e. sucrose, supplied has been obtained in shake flask cultures, indicating the potential of the organism for production of useful EPS on a large (industrial) scale.

Production of xylanases by immobilized Aspergillus sp. using lignocellulosic waste.

In shake flasks immobilized Aspergillus terreus and Aspergillus niger produced 29 IU/ml, 26.7 IU/ml xylanases at 10 mg/ml, 14 mg/ml wheat bran concentration after 48 and 60 h of incubation at 37 °C respectively. In repeated batch fermentation of immobilized Aspergillus sp. the same biocatalyst could be used for three successive cycles.