Kinetics of Bio-Hydrogen Production from Crude Glycerol by Locally Isolated Klebsiella pneumonia via Dark Fermentation

Abstract

Abstract Bioconversion of crude glycerol (CG) to bio-hydrogen (Bio-H2) is promising because the capital investment and operation is cheaper. It is an environmentally friendly approach for waste reduction and clean energy production. However, the selection of microbes that can efficiently metabolise CG under anaerobic conditions is limited. This results in the low production and yield of Bio-H2. Hence, this study sought to examine a new indigenous bacteria (Klebsiella pneumoniae strain HS11286) that can consume CG and convert it into Bio-H2 without the need for pre-treatment or acclimatization. Dark fermentation was employed as it offers advantages in terms of the substrates and producers used. The research focused on the kinetic study for growth and substrate utilisation by kinetic model. In the metabolism of CG by K. pneumoniae, it needed 6 hours for lag phase to adapt to start proliferating and releasing Bio-H2, as well as the metabolites. Based on the HPLC results, three metabolites were produced during the metabolism of CG (i.e.: 1,3-propanediol, propionic acid, and ethanol). The kinetic analysis, and Bio-H2 production were estimated using the kinetic Monod model and the modified Gompertz equation. The kinetic analysis revealed a growth rate (µ) of 0.106 h− 1, glycerol consumption rate (Qgly) of 1.572 g/L/h, and the yield coefficients Yp/x, Yp/s, and Yx/s of 30,758.51 mL/g cell, 479.26 mL/g substrate, and 0.016 g cell/g substrate, respectively. The modified Gompertz model predicted Bio-H2 production of 10,155 mL at 620 mL/h with a 6 h lag period. In conclusion, K. pneumoniae strain HS11286 has the potential to produce almost 10 litre of hydrogen in a short period of time (less than 48 h) without substrate pre-treatment and bacteria acclimatisation or genetic engineering. This study highlighted that the K. pneumoniae strain HS11286 is a promising hydrogen-producer.