Diversity and activity of enriched ruminal cultures of anaerobic fungi and methanogens grown together on lignocellulose in consecutive batch culture

Consecutive batch Cultures (CBC) involving nine serial transfers at 3, 5 and 7 d intervals (2 1 45 and 63 d., respectively) were established to enrich for plant fibre degrading co-cultures of anaerobic fungi and methanogens from rumen digesta. Microbial diversity and fermentation end-products were measured at appropriate intervals over each CBC time-course. While methanogenic populations remained diverse, anaerobic fungal diversity was related to transfer interval and appeared to decrease with increasing transfer number. Acetate was the principal aqueous fermentation end-product With minimal quantities of lactate and formate detected. Methane and carbon dioxide were detected in the gaseous head-space of all co-cultures and the total amounts of gas generated per transfer was greater with transfer intervals of 5 and 7 d compared with a 3 d interval, although the 3 d interval tended to be more efficient per unit time. In conclusion, rapidly growing, methane producing co-cultures of anaerobic fungi and methanogens from rumen digesta were easy to establish on lignocellulose (barley straw) and maintain over considerable time periods. These results suggest such co-cultures have potential in industrial scale anaerobic digestion (AD) of highly fibrous Substrates, which are resistant to degradation in conventional AD plants. (C) 2009 Elsevier Ltd. All rights reserved.