Fermentative Conversion of Cellulose to Acetic Acid and Cellulolytic Enzyme Production by a Bacterial Mixed Culture Obtained from Sewage Sludge

Abstract

A simple procedure that uses a cellulose-enriched culture started from sewage sludge was developed for producing cellulolytic enzymes and converting cellulose to acetic acid rather than CH 4 and CO 2 . In this procedure, the culture which converts cellulose to CH 4 and CO 2 was mixed with a synthetic medium and cellulose and heated to 80°C for 15 min before incubation. The end products formed were acetic acid, propionic acid, CO 2 , and traces of ethanol and H 2 . Supernatants from 6- to 10-day-old cultures contained 16 to 36 mM acetic acid. Cellulolytic enzymes in the supernatant were stable at 2°C under aerobic conditions for up to 4 weeks and had the ability to hydrolyze carboxymethyl cellulose, a microcystalline cellulose, cellobiose, xylan, and filter paper to reducing sugars.