Thermostable Lipase Production By Geobacillus Thermodenitrificans In A 5-L Stirred-Tank Bioreactor

Abstract

Lipases from thermophiles have gained interest in recent years as it has various applications in industries. It plays a significant role in industries as it has high stability and resistant to chemical denaturation. Its extensive application in industries requires its production in a large scale. In this study, thermostable lipase production by Geobacillus thermodenitrificans in a 5-L stirred tank bioreactor was evaluated. The cultivation was carried out for 96 hours at 55 oC in a cultivation medium containing (%; w/v or v/v): glucose 1.0; yeast extract 1.25; NaCl 0.45 and olive oil 0.1. Optimization of physical parameters in the bioreactor will improve the production of the thermosatble lipase. Different physical parameters affecting enzyme production and biomass concentration such as agitation rate (100, 200, 300, 400 and 500 rpm), aeration rate (1, 2, 3 and 4 lpm) and inoculum concentration [0.5, 1.0, 1.5, 2.0, and 2.5% (v/v; 5 x 10 cell/ml)] were evaluated. Thermostable lipase activity was enhanced by 53% in the bioreactor and the biomass concentration increased by 23% after optimizing the physical parameters in the stirred tank bioreactor. Maximum lipase activity of 180 U/ml was obtained at 72 hours of cultivation at 2 lpm, 400 rpm and 2% (v/v; 5 x 10 cell/ml) inoculum with a specific activity of 3.62 U/mg. Thermostable lipase production in the bioreactor was about six-fold higher than that attained in a shake flasks culture. From the results obtained in this study, it is possible of producing thermostable lipase in a large-scale which has an extensive application in industry.