Hydrolysis of microalgal biomass using ruminal microorganisms as a pretreatment to increase methane recovery

•Microalgal cell disruption by ruminal microorganisms was studied.•An enrichment of microorganisms solubilizing algal biomass was conducted.•Microalgae to ruminal fluid ratio influences the hydrolysis and methane production.•The microalgae hydrolysis and methane production were obtained in only 7 days.

The use of ruminal fluid as a source of hydrolytic microorganisms for the pretreatment of a native consortium of microalgae (essentially Senedesmus) was investigated. The hydrolytic enzyme activity of the ruminal culture was first enriched in a bioreactor. Then, using the enriched culture, the effect of the microalgae to the ruminal fluid ratio (S/X) on the hydrolysis and subsequent production of methane was investigated. An S/X ratio of 0.5 showed the best hydrolysis efficiency (29%) reaching in a second stage process a methane yield of 193 mL CH4 g COD−1. The processing time (pretreatment plus methanization) was only 7 days. The predominant ruminal hydrolytic bacteria selected in the enrichment were principally Clostridium, Proteocatella and Pseudomonas.