Fig. 1

a Cellulase activity and biogas production in induced and non-induced samples. a Cellulase activity in the induced sample (filled circle) and the non-induced reference sample with the original chemically defined medium (open circle). Dotted arrows indicate samples compared over time in the induced sample, and over space against the non-induced reference sample. b Gas production in the two samples over the same time period, indicating viable microbial communities. The higher gas production in the cellulase-induced sample (filled circle) is simply due to higher organic load