Kinetics Studies Impact of Initial pH and Addition of Yeast Saccharomyces cerevisiae on Biogas Production from Tofu Wastewater in Indonesia

The purpose of this work was to study the effect of initial pH and yeast Saccharomyces cerevisiae on biogas production from tofu wastewater (TW). The initial pH was varied in ranging of 5 – 9 in substrate without yeast (T5-T9) and with yeast (TY5-TY9). The results showed that optimum initial pH was 8. The maximum biogas was resulted in T8 (275 mL) and TY8 (421 mL). Yeast addition increased total biogas compared with no yeast addition. Kinetic of biogas production was modeled through modified Gompertz and Cone models. The predicted biogas in Cone model was more precise than that in modified Gompertz. The difference between measured and predicted biogas in Cone and modified Gompertz models was 0.193 – 2.809 and 0.316 – 3.115 % respectively. The presence of yeast increased the kinetic constant of ym (biogas potential, mL) and λ (lag period, days), and decreased khyd (hydrolysis rate, /day).