Medium optimization of protease production by Brevibacterium linens DSM 20158, using statistical approach

Various cultivation parameters were optimized for the production of extra cellular protease by Brevibacterium linens DSM 20158 grown in solid state fermentation conditions using statistical approach. The cultivation variables were screened by the Plackett-Burman design and four significant variables (soybean meal, wheat bran, (NH4)2SO4 and inoculum size were further optimized via central composite design (CCD) using a response surface methodological approach. Using the optimal factors (soybean meal 12.0g, wheat bran 8.50g, (NH4)2SO4) 0.45g and inoculum size 3.50%), the rate of protease production was found to be twofold higher in the optimized medium as compared to the unoptimized reference medium.

Some enzymatic properties of cholesterol oxidase produced by Brevibacterium sp

In this study we determined some properties of cholesterol oxidase from a "Brevibacterium" strain isolated from buffalo's milk and identified the cholesterol degradation products by bacterial cell. A small fraction of the enzyme synthesized by cells cultured in liquid medium for 7 days was released into the medium whereas a larger fraction remained boud to the cell membrane. The extraction of this fraction was efficiently accomplished in 1 mM phosphate buffer, pH 7.0, containing 0.7(per cent) Triton X-100. The enzyme stability under freezing and at 45ºC was imrproved by addition of 20(per cent) glycerol. The optimum tempereature and pH for the enzyme activity were 53ºC and 7.5, respectively. The only steroidal product from cholesterol oxidation by the microbial cell and by the crude extract of the membrane-bound enzyme was 4-colesten-3-one. Chromatographic analysis showed that minor no steroidal compounds as well as 4-colesten-3-one found in the enzyme in the buffer solution. Cholesterol oxidation by the membrane-bound enzyme was a first order reaction type