Protease production by thermophilic fungi

Abstract

Submerged cultures of 10 thermophilic fungi, grown at 45° in a medium containing 4% casein, 0.4% glucose, 0.3% yeast extract and salts, were surveyed for extra- and intra-cellular protease production. The yield, thermostability, pH optimum, and inhibitor sensitivity of the crude proteases were determined in each case. The inhibitors used were diisopropylfluorophosphate (DFP), ethylenediaminetetraacetic acid (EDTA), and p-chloromercuribenzoate (pCMB).Seven of the thermophiles produced a substantial quantity of protease, particularly extracellular protease. In comparison to mesophilic fungi most proteases appeared to be unusually thermostable. Neutral and alkaline proteases were most common, as were proteases inhibited by DFP and pCMB. Finally in most of the cases a sensitivity to more than one inhibitor indicated the existence of more than one type of protease.