Effect of agitation rate on biomass and protease production by a marine bacterium Vibrio harveyi cultured in a fermentor

Abstract

A marine bacterium Vibrio harveyi was adapted to grow and produce extracellular proteases in a seawater/Zobell-based medium, supplemented with skim milk under different hydrodynamic conditions, namely agitation and aeration rates. The addition of skim milk to Zobell medium enhanced fivefold the extracellular enzyme production. Protease production seemed to take place after maximum luminescence had been produced. Specific growth rate increased as a consequence of increasing agitation rates. The maximum activity of 4.28 units mg−1 protein were formed with 700 rev min−1 and 0.5 v/v/m. Protease activity detected has a molecular weight of 34 kDa. Another minor band of protease activity was found at 40 kDa.