Understanding working conditions for Entererococcus sp. L1 on methane production: A low temperature condition-based biogas production experiment

To provide an elaborate understanding on the performance of Entererococcus sp. L1 in biogas production at different fermentation periods under controlled low temperature, biogas optimization experiments was undertaken. Specifically, microscopic and culture techniques, physiological and biochemical studies, and measurement of optical densities at 600 wavelengths (OD600) were undertaken to identify and characterize the Entererococcus sp. L1. The aim was to identify the strain and determine its optimum working conditions in biogas production at different fermentation periods under controlled low temperature. The result confirmed the strain as hydrogen-producing bacteria (Enteroccus sp. L1). It was also confirmed that the organic nitrogen source was significantly better than the inorganic nitrogen source in supporting the growth of the bacteria. The optimal pH and temperature for the growth and biogas production performance of the Entererococcus sp. L1 was 7 and 15 °C respectively. The Na2HPO4 concentration of 0.2% was confirmed to be best for the optimum growth of the bacteria, and addition of citric acid resulted to significant inhibitory effect on the growth of the Entererococcus sp. L1. The effect of adding different concentrations (0, 1%, 5%, 10%) of the L1 bacteria inoculum on cow dung at simulated low temperature (15 °C) biogas fermentation showed that 10% treatment had the highest gas production of 3121 ml, which was 89% higher than the control (0 concentration). The daily gas production rate was 0.02 m3/(m−3d−1), which was 90% higher than the control. This showed that 10% treatment provided the best gas production result, with highest gas production occurring at 10% treatment within 31–60 days of fermentation (p