Anaerobic bacteria, cellulolytic systems

The degradation of cellulose by bacterial systems occurs both aerobically and anaerobically. The aerobic bacteria include Acidothennus cellulofyticus, CeUulomonas sp.. Bacillus sp.. Pseudomonas sp., CelMbrio sp., Cytophaga sp., Microbispora sp., and Thermomonospora sp. The anaerobic bacteria arc Acetivibrio cellulofyticus, Bacteroides sp., Clostridium sp., Ruminococcus sp., and Micromonospora sp. This review will cover some mesophilic and thermophilic cellulolytic bacteria, some of which have been reviewed by Ljungdahl and Eriksson (i), Coughlan and Ljungdahl (2), and Robson and Chambliss (5). 

The cellulolytic systems of anaerobic bacteria have been reviewed recently by Goughian and Ljungdahl (2). We shall concentrate on the transcription regulation systems of Acetivibrio cellulofyticus, Bacteroides sp., C. thermoceUum and Ruminococcus sp. 

As referred previously, two main types of cellulolytic systems are currently recognized. Those based on free , soluble enzymes, produced mostly by aerobic microbes that secrete individual cellulases, which act synergistically on native cellulose and those based on complexes of cellulolytic enzymes, or cellulosomes , produced by some anaerobic bacteria and fungi, which are usually attached to the outer surface of the microorganism [40, 101]. CBMs play a role in the phase transfer of a soluble free enzyme onto the insoluble substrate [68, 69]. CBMs are present in several polysaccharide-degrading enzymes, namely in hemicellulases [56, 58, 102], endomannanases [12], xylanases [56, 103], acetyl-xylanesterases [104] and )3-glucosidases [71]. 

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