Process parameter studies by central composite design of response surface methodology for lipase activity of newly obtained Actinomycete

Actinomycete strains from cottonseed soap-stock (a dark gelatinous waste from oil refinery) were obtained. Cultures were analyzed for the enzyme lipase, protease and cellulase production using plate assay(s). Best lipolytic isolates were further quantitatively analyzed for lipase production, using substrate p-nitrophenyl palmitate (p-NPP). Cultures were characterized by morphological and molecular studies. The potent lipase producing strain of actinomycete was optimized for pH, temperature, inoculum size, carbon and nitrogen sources. Further, the lipolytic strain of actinomycete was grown on synthetic media and growth factors were optimized by RSM (Response Surface Methodology) for maximum production of lipase. Total 49 cultures were obtained from enriched soap-stock samples; among them 7 isolates were strains of actinomycete. Potent actinomycete strains were identified as Nocardiopsis alba, Streptomyces leeuwenhoekii, Streptomyces caelestis, Streptomyces werraensis and Streptomyces sclerotialus. Based on quantitative lipase production study, Nocardiopsis alba was selected as the best lipase producer. Optimized results of process parameter studies for lipase production by Nocardiopsis alba were: 5mL inoculum size, temperature 40°C, shaking at 130 rpm, pH 8.0 and cottonseed oil as the best carbon source. Cottonseed oil, K₂HPO₄ and cellulose were noted as main factors as optimized by Central Composite Design (CCD), where the culture showed highest (65.78 U/mL/min) lipase production. Findings of the research would offer potential environmental benefits along with socio-economic benefits if implemented suitably. © 2021 Elsevier B.V.