SINGLE-STEP BIOCONVERSION OF PALM OIL MILL EFFLUENT FOR BIOETHANOL PRODUCTION IN STIRRED TANK BIOREACTOR
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies-II: Energy Production (T1-5P)
Keywords: Oil palm industrial waste, bioethanol, bioconversion, stirred tank bioreactor, optimization
In Malaysia, the oil palm industries produce about 10 million tonnes of palm oil mill effluent (POME) per year. POME is a mixture of high-polluted effluent (from sterilizer and oil room) and low polluted effluent (steam condensate, cooling water, boiler discharge and sanitary effluent), which effects are contributed in serious environmental problems through the pollution of water bodies. There is no suitable and sustainable developed technology yet focused on process development and improvement to utilize such organic residue for value added applications. As the nutrient contents of POME are sufficient for microbial growth it seems to be potential resource for product recovery by liquid state bioconversion. Therefore operating conditions of the stirred tank bioreactor are required to maximize the production of bioethanol utilizing POME as substrate by lignocellulolytic fungi and yeast in single-step bioconversion process.
The bioethanol production was conducted by utilizing agriculture waste, palm oil mill effluent (POME) with the aid of mixed cultures such as T. harzianum, P. chrysosporium, M. hemaelis and yeast, Saccharomyces cerevisiae. Palm oil mill effluent (3-5% TSS, pH 7-8) was collected from oil palm industry, Dengkil, Selangor, Malaysia. The lignocallulolytic fungi and yeast were collected from the lab stock at IIUM for bioethanol production throughout the study. The fungi and yeast were maintained on potato dextrose agar (PDA) plates for the production of cultured inoculum. Simultaneous inoculation of T. harzianum and S. cerevisiae was found to be the potential mixed culture which yields was maximum (ethanol). Statistical optimization was carried out to evaluate the operating conditions of the stirred tank bioreactor for maximum bioethanol production by 2-level fractional factorial design with one central point. The polynomial regression model was developed using the experimental data including the effects of linear, quadratic and interaction of the factors. The factors involved were partial pressure of oxygen (pO2 %), temperature and pH. The other factors substrate (POME) and co-substrate (wheat flour) concentrations, inoculum and agitation were optimized from previous study. The optimization of single-step bioconversion was carried out in a 2L stirred-tank bioreactor applying the mixed culture system. Statistical analysis showed that the maximum ethanol production of 12.5% (v/v) was achieved at temperature of 32.5˚C, pH 3 and pO2 of 20%. The result with the developed process conditions indicated that the maximum production was increased from 12.5 % (v/v) to 12.8 % (v/v) with 63.1 % of the removal of chemical oxygen demand (COD).
