Screening and statistical optimization of media ingredients for production of microbial transglutaminase

Transglutaminase is a calcium dependent enzyme that catalyses acyl transfer reactions between primary amino groups and protein bound glutamine residues. Eighteen bacterial and twenty eight actinomycetes were screened for the presence of transglutaminase. Among the microbial cultures screened Streptomyces sp. D1, showed maximum transglutaminase activity. In this study characterization of transglutaminase and its application to modifying the properties of panner (Indian cottage cheese) in the form of cross linking was investigated. Optimum temperature and pH for enzyme was found to be at 50°C and 6.0, respectively. Optimization of media ingredients for maximizing the transglutaminase activity using Streptomyces sp. D1 was carried out using central composite design. Response surface methodology was employed to standardize the optimum media composition for maximum enzyme activity. Three factors such as carbon source, nitrogen source and pH were tested for the maximum enzyme activity as response. The optimized medium with sugarcane molasses as carbon source 6.0% (w/v), peptone as nitrogen source 1.75% (w/v) were found to be optimal at initial pH 6.5 and incubation temperature 30.0°C with agitation at 100 rpm for 96h. The enzyme activity of transglutaminase obtained from the optimized medium was found to be 4.1 (AU/ml). Low cost substrate such as sugarcane molasses in the form of a renewable substrate is proposed to be suitable even for scale-up production of enzyme and for industrial applications. The ethanol fractionated transglutaminse treated milk was found to produce more paneer with increased moisture content while reduction in cooking loss of the paneer prepared using enzyme treated milk is also reported.