Biodiesel from palm waste cooking using immobilized lipase in modified PVA-alginate sulfate beads

Abstract

Malaysia is currently the world’s second largest palm oil producer, which accounts for 39% of world palm oil production. About 0.5 million tonnes of waste cooking oil is generated annually in Malaysia. Improper disposal of waste cooking oil leads to the environmental pollution particularly in land and water. To overcome these problems, this study aimed to use palm waste cooking oil as a feedstock to produce biodiesel as an alternative to the limited and non-renewable sources of conventional petroleum. Apart from that, utilization of lipase as biocatalyst to produce biodiesel has advantages over chemical catalyst as the reaction can be performed under mild conditions and simple separation process. This study investigated the production of biodiesel from palm waste cooking oil using immobilized Candida rugosa lipase (CRL) in Polyvinyl Alcohol (PVA) alginate sulfate beads. The One-factor-at-a-time (OFAT) method was used in order to select a suitable range of variables before statistical analysis was performed. The Design-Expert software was used as a statistical tool to operate Central Composite Design (CCD) for optimization of significant factors. The statistical analysis was used in order to achieve maximum biodiesel production and evaluate the effect of each variable and their interaction of biodiesel yield. Four main parameters responsible for the yield of transesterification were analyzed; waste cooking oil (WCO) to methanol ratio, temperature, water content and enzyme content. The experimental results showed that the highest conversion was 85.14% under condition oil to methanol ratio 7:1, 10% of water content, 40% wt of enzyme loading and temperature 37.5ºC. The regression model of the ANOVA was found to be significant with p<0.001 and R2= 0.9737. As a conclusion, the results proved that the immobilization method of C. rugosa lipase in PVA-alginate-sulfate beads is reliable and can enhance conversion of palm waste cooking oil to biodiesel.