Biogas production from paper waste by thermophilic bacterial coculture

Abstract

Two of 123 strains of the thermophilic cellulolytic bacteria were selected and named C23 and C73.The fermentation products of cellulose were acetate j and carbon dioxide. Three of 147 strains of the thermophilic methanogens were selected and named M38, M47, and M48. They all utilized carbon dioxide and acetate as substrates for methane production. The fermentation of pure cellulose by thermophilic cellulolytic bacteria in the absence and presence of thermophilic methanogens was studied. In the monoculture, millimoles of products per gram of cellulose fermented were : acetate, 0.523-0.605; and carbon dioxide, 10.8-13.8. In the coculture of cellulose fermentation, the amounts of volatile fatty acids (acetate, propionate, and butyrate) were determined. Acetate was the only volatile fatty acid found. Acetate and carbon dioxide contents decreased whereas substantial amounts of methane were produced (4.73-6.54 mmol/g cellulose). In the fermentation of paper waste, the monocultures of the thermophilic cellulolytic bacteria strain C23 and C73 produced 1.04-1.16 mmol acetate/g paper waste and 10.95-13.40 mmol carbon dioxide/g paper waste. In the presence of thermophilic methanogens, acetate and carbon dioxide decreased in all six coculture combinations, and methane was formed at 4.97-6.73 mmol/g paper waste. Among the six combinations for biogas production, the coculture of thermophilic cellulolytic bacteria strain C23 and thermophilic methanogen strain M4 8 produced the highest amount of methane. The pair would be suitable for further investigations in paper waste treatment for biogas production.