HighlightsA rapid dye based plate screening method for nitrile hydrolyzing enzymes.Method identifies the end products of nitrile hydrolyzing enzymes.The method differentiates between nitrile hydratase and nitrilase producing bacteria.A potential NHase producing bacterial strain was identified as Rhodococcus rhodochrous.

Nitrile hydratase is an enzyme which catalyze the hydration of nitriles into amide and their role as catalysts for acrylamide production in industries are well known. The present study aims at statistically optimizing physiological and nutritional parameters for NHase production from Rhodococcus rhodochrous (RS-6). The effect of incubation period, temperature, pH, carbon and nitrogen sources on the production of NHase was investigated by one factor at a time strategy. Further optimization process was carried out by response surface methodology for studying the interactive effect of these variables using central composite design. The optimized levels of variables obtained by statistical analysis were: incubation period 48 h, temperature 33 °C, pH 7.0, glycerol 1% and urea 0.75%, which resulted in maximum NHase production. The results of ANOVA were significant with the F -value of the model being 296.78, value of R 2 is 0.9983 and the lack of fit test was not significant. The contour and response surface plots showed significant interaction between the variables. The NHase yield was enhanced up to 6.22 fold by statistical optimization using RSM. Thus, the developed experimental design is effective towards process optimization for NHase production from R . rhodochrous (RS-6).

Fusarium culmorum (ASP-87) isolated from tropical soil was investigated under solid state fermentation on a laboratory scale using sixty five (65) agro based materials. Among the different agro based materials evaluated, soybean meal supported maximum L-asparaginase production (7.21 U/gds). Various optimization strategies for the production of L-asparaginase were also carried out with soybean meal and it was observed that inoculum size of 1 × 10 8 spores/mL, day 6 of incubation period, 3 mm of particle size of the substrate, moisture content of 70%, initial pH of 7.0 and temperature at 30°C were found to be optimal for Lasparaginase production. Supplementation of glucose (0.1%) and ammonium chloride (0.1%) enhanced L-asparaginase production to 1.7 fold. Mixed substrate fermentation using soybean meal and wheat bran in the ratio (1:1 w/w) further enhanced production of L-asparaginase to 0.5 fold with a final yield of 18.91 U/gds.

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Three hundred and sixty four (364) isolates of tropical soil fungi were screened for L-asparaginase production by rapid plate method using modified Czapek-Dox agar containing L-asparagine, and either bromo cresol purple or phenol red dye as an indicator. Results of the study revealed that total one hundred and thirty five (135) isolates showed positive reaction for L-asparaginase production as indicated by the color change in and around the colonies between 48 -72 hours of incubation at 28 0 C. A comparative study of the two indicator dyes with varying concentrations showed bromo cresol purple is a better and efficient indicator for L-asparaginase screening than phenol red. Quantitative estimation of L-asparaginase in the selected fungi showed Aspergillus sp. and Fusarium sp. were good candidates for L-asparaginase production.