A simulation model of organic-matter anaerobic degradation suggested earlier was used to describe the acidogenesis phase of glucose anaerobic conversion. It was calibrated on the experimental data of Zoetemeyer et al. (1982), where a continuous-flow, stirred-tank reactor inoculated with activated sludge was studied at different feed flow rates with the pH values controlled by automatic titration. The model considered the different fermentation pathways using two groups of acidogens. It was shown that competition between hydrogen-producing and hydrogen-utilising acidogenic bacteria for glucose causes a hydrogen partial pressure decrease at a decrease of feed flow rate.