Cellulose is the major carbon substrate entering treatment plants for municipal waste waters. In the present investigation an attempt was made to study its degradation in activated sludge. Cellulolytic micro‐organisms were enumerated in different treatment plants and at one plant they were assessed after different steps over a period of about 1 year. The degradation of cellulose contained in Nylon bags suspended in the mixed liquor was also studied and the activities of cellulase components were assayed. Finally, the concentrations of cellulose and lignin in the suspended solids taken from different treatment steps were determined. The results showed that active cellulolysis occurred in activated sludge. The degradation was mainly bacterial, although no significant enrichment of such bacteria was found in the sludge floc. Cellulase activity, however, showed an increase. Experiments with the Nylon bag indicated that 60% of the weight of cotton wool was degraded in 4–5 weeks. It was concluded that about 60% (w/w) of the cellulose entering the system could be degraded by bacteria during aerobic treatment, while 50–60% of that present in the surplus activated sludge was degraded during anaerobic sludge digestion.

Several strains of bacteria of the genus Zymomonas were examined with respect to their potential for higher alcohol synthesis. All strains studied were able to produce higher alcohols during growth in a simple medium containing glucose and yeast extract. The higher alcohols produced were mainly n-propanol and /so-amyl alcohol. In contrast to Saccharomyces cerevisiae, only trace amounts of higher alcohols were produced from glucose by resting cells. When amino acids or other precursors were added to the fermentation medium, the resting cells formed higher alcohols. The stimulation of n-propanol synthesis by precursors was the most pronounced. The results obtained indicate that, with minor differences, the mechanisms of higher alcohol synthesis are comparable to these used by yeasts.

An aerobic mesophilic Pseudomonas sp. isolated from activated sludge degraded different cellulosic materials to varying‐degrees. The degradability was mostly influenced by the lignin content and the crystalline nature of the substrate. Filter paper and cotton fibres, containing little lignin, were degraded maximally. Lignin‐rich Pinus and Larix needles were digested to a lesser extent. There was a difference between natural substrates and substrates that had undergone industrial treatment. At maximal protein production, the isolate converted 11–40% (w/w) of cellulosic substrates into proteins. Alkali treatment of the substrates had only little effect. Cellulose contained in pig‐waste was also degraded by the isolate. At first there was a period of protein production, but after long incubation, the efficiency of conversion of cellulose to protein decreased.

Cellulolytic aerobic bacteria were isolated from activated sludge systems. Of the media tested for enumeration, only filter paper media gave reliable counts. Five isolates were studied further for characterization. It was found that one strain (DK) belonged to the genus Cellulomonas. The other four strains expressed similarity to the genus Pseudomonas. The different characteristics that were studied, however, do not permit them to be identified with any recognized species. Based on certain characters we believe that they are alcaligenes‐like pseudomonads.