METHODS: Simultaneous optimization of biomass and protease biosynthesis by a local isolatedPseudomonassp. — Selection of main medium components and operating conditions

Abstract

The kinetics of cell growth and protease production, substrate specificity, morphology, motility, and antimicrobial effects against food pathogens were evaluated for a Pseudomonas strain recently isolated from fresh cabbage. Protease and biomass production in batch fermentation were tested in relation to different medium components (glucose, meat peptone, NaCl, Ca2+, and Mg2+ content) and in different pH, temperature, and agitation-speed conditions, first by a rapid prescreening assay and then a Plackett-Burman (PB) experimental design. The prescreening assay aimed to determine optimal lower and upper values of each one of the above variables, thereby avoiding estimations or reliance on published data on known Pseudomonas strains. The combination of prescreening and the PB design allowed determination not only of optimal ranges for each of the studied variables but also the significant relevance of each, in rapid, economical fashion. Results showed that temperature, agitation speed, NaCl, and pH had the greatest effects on proteolytic activity, while temperature, glucose, pH, peptone, and agitation speed most significantly affected microorganism growth. This information is useful for maximizing Pseudomonas sp. growth and protease production through optimal operating conditions and media composition. The significant factors identified in this work have been evaluated in a previously published study of medium optimization through use of response surface optimization (Kotlar et al, Ind Biotechnol 6[6] 364-374 [2010]).