Abstract:
This research was to study the alkaline protease production from bacteria isolated from
soil in Thailand byobservation the appearances of clear zone around bacterial colony on BMSM
agar, pH 10, and comparing the crude enzyme activity obtained from culture brothof BMSM, pH
10, at 37 ºC. The results indicated that six bacterial isolates including of 012, 013, 032, 042, 053,
and 071 showed the highest alkaline protease activity at 48 h. After the optimization of enzyme
production in 500 mL-baffle flask, bacteria isolate 032 produced the highest activity when
cultivated in BPMM medium, pH 10, with dextrin and soybean meal as carbon and nitrogen
source at 37 ºC. The strain was identified by 16S rDNA sequencing analysis as Bacillus cohnii at
98.27 % similarity. The efficiency of various cultivation techniques for alkaline protease
production from B. cohnii were observed in 5-L fermenter. The results revealed that cultivation of
B. cohniiusing fed-batch fermentation technique in BPMM medium, pH 10, containing dextrin
and soybean meal as carbon and nitrogen source with non-substrate adding and non-pH
controlling, at 37 ºC, aeration rate 1 vvm, agitation speed 500 rpm, feeding with the same medium
concentration when its growth was deceleration phase at dilution rate of 0.90 L/h were the most
suitable. Consequently, the specific growth rate (µ) and specific alkaline protease production rate
(qp
) of 0.124 h-1
and 1.785 U/g cell.h, respectively, and the maximum enzyme activity and
enzyme productivity of 9.51 U/mL and 0.396 U/mL/h that were higher than using batch
cultivation technique for 1.6 times.