Biosynthesis and characterizations of extracellular enzymes of microbial isolates from dairy industrial effluent

Abstract

Diary effluents are environmental pollutant which could serve as source of substrate for microbial enzymes' synthesis. This research investigated the isolation and screening of bacteria and fungi with potential extracellular proteolytic and amylolytic properties from dairy effluents, and their characteristics for maximum enzyme production. Effluent from a dairy industry located in Ibadan, Nigeria, was collected for isolation and screening of microbial species for enzymatic activities. The Biological Oxygen Demand (BOD), Total Soluble Solid (TTS), and pH of the effluent were determined using standard procedures. The potential isolates were characterized morphologically and by molecular techniques. Proteolytic and amylolytic activities of isolates were investigated on skimmed milk starch agar respectively and optimized with varying pH (6.0 - 9.0), temperature (27 - 60 °C) and incubation period (12 - 72 h). Data were analyzed by Duncan Multiple Range Test. Biological Oxygen Demand, Total Soluble Solid and pH of the effluent were 14.67 mg/L, 13.33% and 7.58 respectively. Eleven isolates were positive for either protease or amylase synthesis, but only two showed both proteolytic and amylolytic activities and were molecularly characterized as Bacillus stratosphericus CM2HG6 and Aspergillus welwitschiae. Optimization showed that enzyme production by B. stratosphericus CM2HG6 was highest at 35 °C, pH 7.0 for 48 h, and that of A. welwitschiae achieved optimum production at 37 °C, pH 8.0 for 72 h. Under optimized conditions, Bacillus stratosphericus CM2HG6 was the highest amylase and protease producer (24.4 and 30.74 U/ml respectively), while A. welwitschiae was the lowest producer (12.58 and 18.8 U/ml respectively). The study successfully showed that these industrially-important enzymes can be produced by microbial strains isolated from dairy effluent, and production can be further optimized