초록
Detailed experiments were designed to evaluate the function of load-shock treatment strategy (50 g COD/l; 3 days) for selective enrichment of acidogenic hydrogen (H<SUB>2</SUB>) producing consortia in comparison with untreated anaerobic consortia. Experiments performed in suspended-batch mode bioreactors for 520 days illustrated the relative efficiency of load-shock treated consortia in enhancing H<SUB>2</SUB> production (16.64 mol/kg COD<SUB>R</SUB>) compared to untreated-parent consortia (3.31 mol/kg COD<SUB>R</SUB>). On the contrary, substrate degradation was higher with control operation (ξ<SUB>COD</SUB>, 62.86%; substrate degradation rate (SDR), 1.10 kg COD<SUB>R</SUB>/m<SUP>3</SUP>-day) compared to load-shock culture (52.33%; 0.78 kg COD<SUB>R</SUB>/m<SUP>3</SUP>-day). Fatty acid composition documented a shift in the metabolic pathway towards acetate formation after applying load-shock, which manifests higher H<SUB>2</SUB> production. Microbial profiling documented a significant alteration in species composition of microbial communities after repeated load-shock applications specific to enrichment of Firmicutes which are favourable for H<SUB>2</SUB> production. Dehydrogenase activity was stabilized with each re-treatment, signifying the adaptation inclination of the biocatalyst towards increased proton shuttling between metabolic intermediates, leading to higher H<SUB>2</SUB> production. Voltammograms of load-shock treated cultures showed a marked shift in oxidation and reduction catalytic currents towards more positive and negative values respectively with increasing scan rate evidencing simultaneous redox-conversion reactions, facilitating proton gradient in the cell towards increased H<SUB>2</SUB> production. Load-shock treatment facilitates direct cultivation of inoculums at higher substrate load without any chemical pretreatment. This study documented the feasibility of controlling microbial metabolic function by application of load-shock treatment either for preparing inoculum for startup of the reactor or to the reactor resident microflora (in situ) during operation whenever required to regain the process performance.