Optimization of biological transesterification of waste cooking oil in different solvents using response surface methodology

Abstract

Purpose – The purpose of this paper is to speak about the production of biodiesel from waste cooking oil which serves as an alternate fuel in the absence of conventional fuels such as diesel and petrol. Though much research work was carried out using non-edible crops such as Jatropha and Pongamia, cooking oil utilized in bulk quantity is discarded as a waste. This is reused again as it contains more of esters that when combined with an alcohol in presence of an enzyme as a catalyst yields triglycerides (biodiesel). Design/methodology/approach – The lipase producing strain Rhizopus oryzae and pure enzyme lipase is immobilized and treated with waste cooking oil for the production of FAME. Reaction parameters such as temperature, time, oil to acyl acceptor ratio and enzyme concentration were considered for purified lipase and in the case of Rhizopus oryzae, pH, olive oil concentration and rpm were considered for optimization studies. The response generated through each run were evaluated and analyzed through the central composited design of response surface methodology and thus the optimized reaction conditions were determined. Findings – A high conversion (94.01 percent) was obtained for methanol when compared to methyl acetate (91.11 percent) and ethyl acetate (90.06 percent) through lipase catalyzed reaction at oil to solvent ratio of 1:3, enzyme concentration of 10 percent at 30°C after 24 h. Similarly, for methanol a high conversion (83.76 percent) was obtained at an optimum pH of 5.5, olive oil concentration 25 g/L and 150 rpm using Rhizopus oryzae when compared to methyl acetate (81.09 percent) and ethyl acetate (80.49 percent). Originality/value – This research work implies that the acyl acceptors methyl acetate and ethyl acetate which are novel solvents for biodiesel production can also be used to obtain high yields as compared with methanol under optimized conditions.

Rhizopus oryzae Lipase, a Promising Industrial Enzyme: Biochemical Characteristics, Production and Biocatalytic Applications

“…The former has been used not only with free ROL but with WCBs because it is an easy, fast and cheap immobilisation technique [239]. The most common entrapment strategies are based on polyvinyl alcohol and alginate employment [211,212,223,240]. Muanruksa et al [202] obtained outstanding results with free proROL immobilised into alginate-polyvinyl alcohol beads.…”

“…Several authors have published works in which ROL and stepwise addition strategy have been employed [181,214]. Additionally, other authors have focused on seeking the most adequate acyl-acceptor-the one that has fewer negative effect on the enzyme-by testing different alcohols [204,240] and even the short-esters of the corresponding alcohols performing interesterification reactions [212,215]. Besides, regarding solvents employment, their absence in solvent-free systems has arisen as an interesting operational alternative because of the minimisation of biodiesel downstream processes and the avoidance of hazardous solvents, making the overall biotransformations more cost-effective and environmentally friendly [170,208,215,218].…”

Designing a Domestic Biodiesel Generation Machine for Rural Communities

“…Biodiesel is made under the process called transesterification, where oil goes through five chambers namely: reactor, separator, methanol removal, neutralisation and washing, and finally a dryer. The process allows the removal of the glycerine component of the oil, to allow thinner, less viscous solutions which remain liquid in lower temperatures (Awogbemi et al, 2021d: Balasubramanian, et al, 2016.…”