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Development of acid-base-enzyme pretreatment and hydrolysis processes for enhanced bioethanol production from palm oil mill effluent
International Islamic University Malaysia
xvii, 150 leaves : illustrations ; 30cm.
Palm oil mill effluent (POME) is one of the main agroindustrial wastewater in Malaysia. Highly polluting palm oil mill effluent (POME) is a serious threat to the environment. The methods being used to treat POME are inefficient and complex either in terms of cost or in terms of environmental preservation. The purpose of this study was to develop an effective method to enhance the bioethanol production that uses acid-base-enzyme pretreatment and hydrolysis of POME by locally produced cellulase enzyme. Numerous experiments such as characterization of POME, acid-base-enzyme pretreatment, development of the enzymatic hydrolysis conditions for reducing sugar production, optimization of media and process parameters, and evaluation of bioethanol through liquid state fermentation of hydrolysate of POME by using Saccharomyces cerevisiae were carried out to achieve the objectives of the study. Pretreatment and enzymatic hydrolysis were successfully developed for maximum production of reducing sugar. Statistical analysis in the form of one factor at a time (OFAT) and face centered central composite design (FCCCD) were employed to obtain the optimum media and process conditions for maximum reducing sugar and bioethanol production. Through OFAT as the pretreatment process, the concentration of diluted H2SO4 and its dose, agitation, time, total suspended solids (%TSS), concentration of NaOH, and initial enzyme dose were found to have the most significant contribution toward reducing sugar production in the POME based medium. The OFAT results showed that the highest reducing sugar yield, 23.47 mg/ml of POME was achieved by enzymatic hydrolysis with 5% (w/v) of pretreated POME, pH of 6, 150 rpm of agitation and 80U of cellulase enzyme with the stock enzyme activity of 40U/ml CMCase after 18 hours of incubation. Based on OFAT results obtained, optimization of two factors such as substrate concentration and enzyme loading were carried out by applying the face centered central composite design (FCCCD) under the response surface methodology (RSM) to develop a second-order regression model successful improvement in the production of reducing sugar was achieved. The optimum reducing sugar production was 26.57 mg/ml (53.14%), which was attained within 18 hours of hydrolysis time at room temperature (30 ± 2oC), 5% (w/v) of TSS, and 80U of enzyme dose. However, the fermentation process was conducted by OFAT and FCCCD methods to achieve the highest bioethanol production. The highest yield of bioethanol, 6.75 % v/v of hydrolysate POME in the same bioreactor was achieved by an OFAT method with pH 6, 3% (v/v) of inoculum, 72 hours of fermentation time, 25 mg/ml of reducing sugar content and 30oC of temperature. After FCCCD method, the rate of bioethanol production was 7.64% v/v from the fermentation step at optimum conditions. Kinetic studies of the produced bioethanol were also performed and found the specific growth rate (µ) at (0.198 h-1), and the specific rate of product formation at 0.239 h-1 after 3 days of fermentation, respectively. The findings show a positive route on effective and sustainable management of POME through biofuel production that could contribute to the economic development of the country.
Thesis (MSBTE)--International Islamic University Malaysia, 2017.
Includes bibliographical references (leaves 115-136).