Kinetics and statistical optimization study of bio-hydrogen production using the immobilized photo-bacterium

The present study embarked on investigating the photo-fermentative bio-H₂ production kinetics and statistical optimization of operational parameters using immobilized inoculum from dark fermented palm oil mill effluent (DPOME). The statistical optimized values of initial pH, inoculum-substrate percentage (ISP), and light intensity were achieved by implicating the central composite design (CCD) under response surface methodology (RSM). The kinetic evaluation was conducted in terms of H2-yield with ISP ranged from 10 to 30%. The highest H₂ production potential (P) and rate (R_max) of 30.59 ml.H₂/g-COD_removed and 0.514 ml h⁻¹ respectively were achieved with reported lag phase (ρ) value of 32 h by using 20% of ISP. However, an observed R_max of 0.746 with a _ρ value of 39 h was attained at ISP of 15%. The quadratic model developed by using CCD was observed to display the significance value of < 00.5 of probability error. Additionally, observed values of correlation coefficient (R²), adequate precision (AP), and coefficient of variance (CV) for acquired H2-yield were 0.9219, 12.076, and 11.24 ml.H2/g-CODremoved, respectively. Under optimal conditions values (initial pH, 6.0; ISP, 20%; and light intensity, 350% W/m2), H2 yield of 147 ml.H₂/g-COD_removed was achieved from DPOME, while reducing the COD value by 78 percentage. This statistical model is suggested to possess the regression, interaction, and quadratic terms as significant, so it can be deemed acceptable in terms of its achievable reproducibility.