Ajay Pal

Production and extraction optimization of xylanase from Aspergillus niger DFR-5 through solid-state-fermentation.

The effects of solid substrates, initial moisture content, moistening medium, temperature and incubation time on xylanase production by Aspergillus niger DFR-5 was studied and the highest activity (2596 IU/g dry substrate (gds)) was achieved in medium that contained wheat bran (WB) and soybean cake (SBC) at a ratio of 70:30, was moistened to 70% with MSS-2 mineral salt solution, and incubated for 6 days at 40 degrees C. Water at 37 degrees C was suitable for efficient recovery of enzyme from moldy WB-SBC medium. The extraction parameters for xylanase were optimized with respect to minimum volume of extractant using a central composite rotatable design (CCRD). The maximum recovery of xylanase (4465+/-52 IU/gds) with 92.5% desirability was obtained employing water (10 ml/gds) as extractant at 200 rpm for 60 min. The result shows that an overall 5.4-fold increase in xylanase production was obtained in concentrated form by optimizing medium components and extraction conditions.

Efficacy of xylanase purified from Aspergillus niger DFR-5 alone and in combination with pectinase and cellulase to improve yield and clarity of pineapple juice

Pineapple is one of the fruits having xylan rich hemicellulose content more than pectin. Therefore, the efficacy of absolutely purified xylanase from A. niger DFR-5 alone and in combination with pectinase and cellulase on juice yield and clarity was studied. Xylanase provided maximum yield (71.3%) and clarity (64.7%) of juice in comparison to control responses (61.8% yield and 57.8% clarity). When used together, a synergistic effect of xylanase, pectinase and cellulase on process responses was observed indicating the necessity of a cock-tail of hydrolytic enzymes for complete cell wall degradation. Overall, an increase in juice yield by 52.9% was observed. The process was numerically optimized with the constraint of ‘minimum’ pectinase and cellulase and ‘maximum’ xylanase and incubation time for ‘maximum’ juice yield and clarity. The closeness of observed response (90.2% yield and 80.9% clarity) to the predicted one (89.6% yield and 80.3% clarity) indicated the validity of developed model.

Simplification and optimization of deMan Rogosa Sharpe (MRS) medium for enhanced production of bacteriocin by Weissella paramesenteroides DFR-8.

Complex growth medium such as deMan Rogosa Sharpe (MRS) medium, commonly used for cultivation of fastidious lactic acid bacteria (LAB) interfere in bacteriocin purification. Sometimes all the ingredients of a defined medium are not required by all LAB strains for bacteriocin production. In the present study, composition of the MRS medium for the production of bacteriocin by Weissella paramesenteroides DFR-8, an isolate from cucumber (Cucumis sativus), was simplified and optimized with a step-wise strategy. In the first step, production profile, effect of incubation temperature, various C and N sources were investigated. In the second step, central composite rotatable design was employed to decide the optimal concentration of 3 key components (glucose, tryptone and pH) and the experimental results were fitted with a second order polynomial regression equation. According to the set criteria, the predicted bacteriocin titer from a medium containing 7.99% glucose, 9% tryptone, pH 7.5 (91.9% desirability) was 540 AU/ml and the observed bacteriocin titer was 538 AU/ml that indicated the validity of the developed model. Using optimized medium, bacteriocin titer of 674.5 AU/ml could be achieved after 72 h of fermentation that is nearly 2.5 fold higher than that obtained from unmodified MRS medium.