Screening studies on seventy eight strains of Bacillus sphaericus (Bs) of
different origins have revealed that the majority of cultures produced extracellular
alkaline protease activities in' variable levels when grown in nutrient broth- yeast
extract- salt medium (NYSM) under shake culture conditions. Physiological studies on
enzyme formation by two highly mosquitocidal strains namely the international strain
2362 and a local Egyptian isolate NRC 69 have shown that the enzyme was produced
on a variety of different media including standard media, powdered legumes seeds
broths as well as media based on agro-industrial by-products. The highest enzyme
levels were obtained in both Bs cultures upon using fodder yeast, a by-product of
ethanol fermentation industry, as a mono component medium for growth and
ENZYME production. Maximum enzyme levels were obtained in shake cultures with
medium containinJl 4% (w/v) fodder yeast under high aeration levels, inoculum size
ranges 4-8 x 10 CFU/ml after three days of incubation at 30°C. The enzyme
exhibited maximum activity at 55°C incubation temperature and pH 8.5 suggesting an
alkaline protease activity with retention of about 60 % of the activity at pH 10 for the
enzymes of both bacterial strains. Enzyme stability at 60°C was markedly improved in the presence of calcium chloride. lnhibjticn cb~;c.:; ;;hvyycu ii,aHi~ aikanne pr~!c:::!:-:;- --~--
activity was inhibired (72% - 79%) by an active-site inhibitor of serine protease, phenyl methylsulfonyl fluoride (PMSF) but not by soybean trypsin inhibitor or iodoacetamide .. These results suggest that the alkaline protease activity produced belongs to serine protease group of enzymes prevalent in some species of bacilli.