HYDROGEN-PRODUCTION BY THERMOPHILIC ANAEROBIC-BACTERIA CLOSTRIDIUM-THERMOSACCHAROLYTICUM, IMMOBILIZED IN POLYVINYL-ALCOHOL CRYOGEL

Immobilization of Clostridium thermosaccharolyticum cells in a cryogel of polyvinyl alcohol (PVA) has been performed using a 14 - 16 h cultu re characterized by the highest cell capacity for hydrogen production. A comparative study of glucose and xylose catabolism during batch cul tivation of free and immobilized cells shows that the latter are chara cterized by a different ratio of end products: hydrogen and acetate yi elds increase, while that of ethanol tends to decrease. Investigation of glucose (1 - 10 g/liter) catabolism by immobilized cells in a conti nuous culture (retention time 0.8 - 5 h) reveals alterations in the sp ectrum of the metabolites formed and in their stoichiometric ratios in comparison with those of batch cultivated free and immobilized cells. Along with the usually detected products, butyrate formation has been recorded. The biocatalyst based on C. thermosaccharolyticum bacteria entrapped in PVA cryogel retained the capability for production of hyd rogen and other metabolites for at least one year.