Production of cross linked lipase from cocoa pod husk

Abstract

Cocoa pod husk (CPH) is a by-product obtained after removal of cocoa beans from the cocoa fruit which causes many environmental problems. The analysis of CPH has shown that this waste material contains high amounts of protein. Hydrolase is one of the products that can be extracted from the CPH protein. Compared to other enzymes, hydrolases are more frequently used industrially. However, enzymes are biocatalysts that are quite unstable. Hence, cross linked enzyme aggregate (CLEA) is a known powerful tool for improving enzyme performance, stability, selectivity and reusability. In this study, screening and extraction of lipase from cocoa pod husk was performed. The optimum condition of lipase extraction is used for preparation of cross-linked enzyme aggregate. The characterization of free and CLEA lipase regarding stability, reusability and kinetic was carried out and finally CLEA-lipase was applied for biodiesel production from Jatropha curcas oil. In all three stages the optimum condition was achieved using Face centered central composite design (FCCCD) with response surface methodology (RSM). From 20 runs the highest activity for extraction of lipase was 11.43 U/ml (around 2.5 fold increase in lipase production) under the condition of 50mM sodium phosphate buffer pH8 with the ratio of 7% (w/v) CPH. The highest activity for CLEA-lipase at the presence of using 20% saturated ammonium sulfate, 60 mM glutaraldehyde as cross-linker and 0.17 mM bovine serum albumin as feeder. The optimal reaction temperature and pH value in enzymatic reaction for both crude enzyme and immobilized were found to be 45˚C at pH 8 and 60˚C at pH 8.2, respectively. A systematic study of the stability of CLEA and crude enzyme was taken with regards to temperature (25-60 ˚C) and pH (5-10) value and in both factors, CLEA-lipase showed more stability than free lipase. The Km value of CLEA was higher compared to free enzyme (0.55 mM vs. 0.08mM). The CLEA retained more than 60% of the initial activity after 6 cycles of reuse compared to free enzyme. Structural characterization of CLEA-lipase by Field Emission Scanning Electron Microscope (FE-SEM) revealed that CLEA from CPH have spherical appearance. Application of CLEA-lipase for biodiesel production was done and the optimum levels of oil-to-ethanol molar ratio, catalyst loading, reaction temperature, agitation and reaction time were found to be 1:6, 3 (w/w%), 45˚C, 200 rpm and 3 h respectively with 93.86% conversion of Free fatty acid (FFA) in to biodiesel which is obtained from GC-MS. In conclusion, the development of this process would be an alternative source for immobilized lipase production in large scale and cost effective in terms of using a wasteful by-product to produce a recyclable biocatalyst that has a wide range of applications. This study can add for more information on the application of low cost oil (J.Curcas oil), ethanol and using low-cost catalyse (CLEA-lipase from CPH), for the production of renewable biodiesel.