Enhanced production of alkaline protease by Aspergillus niger DEF 1 isolated from dairy form effluent and determination of its fibrinolytic ability

Abstract

Proteases constitute most important enzymes owing to their wide variety of functions and have immense applications in various industries viz., medical, pharmaceutical, biotechnology, leather, detergent, and food industries. Despite of their wide spread occurrence in various sources, microorganisms present remarkable potential for proteolytic enzymes production due to their extensive biochemical diversity and susceptibility to genetic manipulation. The present study was aimed at isolating alkaline protease producing fungal members from dairy form effluents, designing the process variables for maximizing the protease production and determining the fibrinolytic potential of the partially purified alkaline protease. To achieve the specified objectives, the dairy form effluent was processed for the isolation of proteolytic fungi using suitable microbiological medium. All the fungal isolates were screened for their protease producing ability and the isolate showing highest alkaline protease production was selected for further studies. Optimization of different fermentative variables like carbon, nitrogen sources, pH, temperature and incubation period were carried out to enhance enzyme production. Ammonium sulphate fractionation was employed to partially purify the enzyme following which its fibrinolytic potential was determined. Based on morphological and microscopic studies, the selected fungal isolate was identified as Aspergillus niger. Optimization studies using OVAT (one variable at a time) method revealed an enhanced protease production in the presence of fructose as additional carbon source and ammonium sulphate as nitrogen source. The optimum incubation period, temperature and pH for enzyme production by the selected fungal isolate was found to be 92 h, 50°C and 10, respectively. The partially purified alkaline protease was efficient in the removal of blood stains emphasizing its fibrinolytic ability. An alkaline protease producing Fungal sp. was screened and isolated from dairy form effluent and it was found to be efficient in the removal of blood stains proving its fibrinolytic potential. Enzymes produced from microorganisms that can survive under extremes of pH could be particularly useful for commercial applications under high alkaline conditions.