Fresh and Fermented Vegetables as a Source of Proteolytic Bacteria

KOTLAR CATALINA; AGÜERO MARÍA VICTORIA; PONCE ALEJANDRA G; PÉREZ BORLA OLINDA; ROURA SARA INES

Handbook of plant-based fermented food and beverage technology

CRC Press

Lugar: Boca Ratón; Año: 2012; p. 731 - 756

Microbial proteases are among the most important hydrolytic enzymes and have been studied extensively since the advent of enzymology. There is renewed interest in the study of proteolytic enzymes, which not only play an important role in the cellular metabolic process but have also gained considerable attention in the industrial community. Moreover, proteases are the most important category of industrial enzymes, accounting for more than 65% of the total industrial enzyme market. Bacteria, molds, and yeast are some of the microorganisms that are able to produce proteases. Microorganisms elaborate a large array of proteases, which are intracellular and/or extracellular. Intracellular proteases are important for various cellular and metabolic processes, such as sporulation, differentiation protein turnover, maturation of enzymes and hormones, and maintenance of the cellular protein pool. The extracellular ones are important for protein hydrolysis in cell free environments and able the cell to absorb and utilize hydrolytic products. Extracellular protease produc­tion by microorganisms is highly influenced by media components, variation in carbon/nitrogen ratio, presence of some easily metabolizable sugars, such as glucose, and presence of metal ions. Several others factors, such as aeration, inoculums density, pH, temperature, and incubation time also affect the amount of protease production and their interaction plays an impor­tant role in the synthesis of these enzymes. Vegetables are renewable raw materials associated with diverse microbial populations, therefore they could be an interesting and cheap source of proteolytic bacteria. Among vegetables cabbage (Brassica oleracea var. capitata) is a biennial sturdy and inexpensive leafy plant. It is widely cultivated throughout the world and stored so well that it is available all the year round. The aim of the present chapter is to describe the isolation and characterization of extracellular producing bacteria from fresh and fermented cabbage. To select profitable bacteria to apply on different industries, the proteolytic substrate specificity of the isolated bacteria was assayed using different protein sources. Taken into account the uses and the high demand of proteases, there is a need for the research of new strains of bacteria that produce enzymes with novel properties and the development of low cost industrial medium for­mulations. In commercial practice, the optimization of medium composition is done to maintain a balance between the various medium components, minimizing the amount of unutilized components at the end of fermentation. In the light of the above facts, another objective of this study was to optimize the fermentation medium in order to enhance the protease production from two of the strains previously isolated from fresh and fermented cabbage. The optimization of culture medium and cultivation was performed using both conventional methods and the Plackett-Burman (PB) experimental design that is usually applied as a preoptimization stage looking for the study of the statistical factors with significance on the dependent variable. Once the critical components and operating conditions to the protease production were screened, the second stage of the optimization procedure was to find the optimum for maximum product formation. RSM was employed in this second stage to optimize the fermentation medium for enhancing protease production.