Biogas production from cellulose by co-culture

Abstract

Three from 113 strains of the cellulolytic bacteria were selected and named CU1, CU3 and CU4. Acetate, succinate, H₂ and CO₂ were the fermentation products of cellulose. Five from 51 strains of the methanogens were selected and named Sc1, Sc2, Sc3, Sc4 and Sc5. H₂ and may be acetate were utilized for CH₄ production. The fermentation of cellulose by the selected cellulolytic bacteria in the absence and presence of the selected methanogens is described. In the mono-culture, micromoles of products per gram of cellulose fermented were : acetate, 541-547; succinate, 53-83; H₂, 5750-7625; and CO₂, 1760-2220, In the co-culture of cellulose fermentation, acetate was the major acid production (87%), carbon dioxide decreased (455-1650), and hydrogen did not accumulate. Substantial amounts of methane were produced in the co-cultures (1350-2450). The cellulolytic bacteria strain CU1, and the methanogen strain Sc4 were used in the co-culture systems of the fermentation of five kinds of individual substrates (cellulosic wastes), such as pineapple peel, waste paper, straw, Bermuda grass and water hyacinth. In all mono-culture systems, micromoles of product per gram of substrates fermented were: acetate. 116-892 (100%); H₂, 0-6125; and CO₂, 0-1100. In the co-cultures acetate was also the major product (249-757), carbon dioxide decreased (60-1050) and hydrogen could not be detected. Substantial amount of methane were produced in the co-culture (60-2120). The total amounts of fermentation products and degree of cellulose degradation were varied in different kinds of the tested substrate and also in different conditions, i.e., actual and alkali-treated. From five tested substrates, waste paper, the highest cellulose content, was the best substrate for biogas production by the co-culture of the selected strains.