Microcrystalline forms of cellulose as substrates for strains of clostridium thermocellum and cellulase formation

Abstract

Clostridium thermocellum strains ATCC 27405, NCIB 10682 and LQR1 have been examined for saccharification of different forms of cellulose and their ability to produce cellulase. Strain ATCC 27405 was the most effective in metabolising Avicel, filter paper and cellulose CF11 (the most resistant substrate). Strain LQR1 was the least effective, strain NCIB 10682 had an intermediate activity. All strains metabolised cellobiose rapidly but produced a deficient cell-free cellulase, with up to half the potency of that from cellulose-grown cultures. Strains NCIB 10682 and LQR1 secreted three-fold more β-glucosidase than strain ATCC 27405, which however secreted the best cellulase, itself not necessarily related to maximum CM-cellulase activity. Strain ATCC 27405 grown in media MJ, GS-2 or DSM indicated medium MJ produced the most active and stable cellulase over 120 h growth; medium GS-2 produced cellulase more rapidly, of the same activity but of less stability; medium DSM gave cellulase most rapidly, but of lower activity and even greater instability, but accompanied by a 30% conversion of the initial cellulose to sugar.