Optimisation of biohydrogen production by locally isolated Klebsiella sp. strain PR2

Abstract

Nowadays, 80% of the world energy requirement depends on fossil fuels. This ultimately will lead to a reduction in global fossil fuel resources. Hydrogen is a sustainable, clean source of energy and can be produced through biological process by microorganisms. The biohydrogen production is important due to both environmental and economic factors, since waste substrates can be used to generate biogas rich in biohydrogen. The aim of this study was to isolate biohydrogen producing bacteria from agricultural wastewater and to optimise the biohydrogen production using enrichment medium. Out of 25 bacteria obtained, only 13 isolates had the ability to produce biohydrogen. One isolate that produced the highest biohydrogen was selected for 16S rDNA sequence identification. The bacterium was identified as Klebsiella sp. strain PR2. For the optimisation of biohydrogen production, fermentation was carried out in batch culture, where parameters such as carbon and nitrogen source concentration, initial pH of the medium, inoculum size, as well as incubation temperature were investigated. D-mannitol was found to be the best carbon source while peptone was the best nitrogen source for biohydrogen production with concentration of 0.2% (w/v) and 0.5% (w/v), respectively. The optimum condition for biohydrogen production was achieved at the initial pH 8 of the medium, incubation temperature of 30 °C and 10% (v/v) of inoculum. After 24 hours of incubation, the highest yield obtained (YP/X) was 8547.42 g/g while the highest biohydrogen productivity was 177.24 mol/L/h. Biohydrogen production using palm oil mill effluent (POME) as substrate was also conducted. Fermentation was carried out in sterile raw and final discharge POME by inoculating with 10% (v/v) bacteria inoculum and incubated at 30 oC for 5 days. The maximum biohydrogen productivity from raw and final discharge POME were 1.44 mol/L/h and 1.81 mol/L/h, respectively. The highest colour removal were 38% (initial: 18167 ADMI) for raw discharge POME and 31% (initial: 1873 ADMI) for final discharge POME were obtained after 5 days of treatment. Meanwhile, the highest COD removal were 34.8% (initial: 7320 mg/L) and 50.8% (initial: 1410 mg/L) for the raw and final discharge POME, respectively. From this study, it could be concluded that Klebsiella sp. strain PR2 has potential applications for biohydrogen production utilising POME as substrate besides treating the POME through biodegradation process.