Application of rumen microorganisms for enhanced anaerobic degradation of bagasse and maize bran

Batch and continuous culture experiments with rumen microorganisms were carried out in order to study the anaerobic conversion of maize bran and bagasse. Within a pH range similar to that of the rumen at 39°C and a substrate concentration of 20 g total solids per litre in batch cultures, maximum degradations of 49 and 52% of the total fibre fractions of maize bran and bagasse, respectively, were obtained after incubating for 168 h. Total production of volatile fatty acids (VFA) and methane per gramme volatile solids (VS) digested in 7 days were 11.85 mmol and 0.077 1 for bagasse and 10.38 mmol and 0.064 1 for maize bran, respectively. At loading rates between 20 and 35 g total solids per litre per day, and solid and hydraulic retention times of 60 and 19 h, respectively, total fibre degradation was in the range 54–69% with around 30% apparent loss of lignin. Average productions of VFA and biogas per gramme VS digested per day varied between 6.45 and 7.75 mmol and 0.06 and 0.191, respectively. The continuous culture system appeared to perform better than batch cultures in converting agro-industrial residues to VFA which are substrates of methanogenic bacteria. It is suggested that the artificial rumen reactor be used in combination with a high-rate methanogenic reactor as means of efficient anaerobic conversion of bagasse and maize bran to methane.