Bioaugmentation Strategies to Improve Cellulolytic and Hydrogen Producing Characteristics in CSTR Intermittent Fed with Vegetable Kitchen Waste and Napiergrass

Kitchen waste recovery in Taiwan has achieved 1/3 population equivalent and the characteristics of kitchen waste contained high organic substance make it a promising substrate for biohydrogenation. However, the hydrolysis of cellulosic biomass is the rate-limiting step in biohydrogenation process. As a result, the enrichment of cellulolytic consortia and bioaugmentation are crucial to improve biohydrogenation performance. In this study, enrichment strategy and bioaugmentation were adopted in a 3-L biohydrogen and a 10-L biomethane reactor fed with vegetable kitchen waste and napiergrass. The volumetric loading rate was controlled at 20 and 4 kg-COD m -3d -1 with hydraulic retention time of 4 and 20 day respectively. Influent composition of napiergrass and vegetable kitchen waste was increased from 1:1 to 3:1 to enhance the cellulolytic characteristics in enrichment phase. The COD removal efficiency in biohydrogen reactor decreased from 10% to 6.4% indicating the refractory cellulosic biomass cannot be effectively converted in biohydrogen reactor. Enriched Clostridium sp. TCW1 which is an anaerobic-thermophilic bacterium was introduced in the bioaugmentation phase. This study revealed that this strain can convert cellulose into acetate and butyrate with up to 90% conversion efficiency. DGGE fingerprints also indicated Clostridium sp. TCW1 can sustain in both reactors.