Sustainable Refining of Vegetable Oil Made Easy with a Designer Phospholipase C Enzyme

Evaluation of Microbial Phospholipase and Lipase Activity Through the Chromatographic Analysis of Crude, Degummed, and Transesterified Soybean Oil for Biodiesel Production

The present study aimed at synthesizing fatty acid methyl esters in a combined enzymatic method by applying degumming and transesterification of soybean oil. A soluble lipase from Serratia sp. W3 and a recombinant phosphatidylcholine-preferring phospholipase C (PC-PLC) from Bacillus thuringiensis were used in a consecutive manner for phosphorus removal and conversion into methyl esters. By applying 1% of recombinant PC-PLC almost 83% of phosphorus was removed (final content of 21.01 mg/kg). Moreover, a sensitive and selective high-performance liquid chromatography method coupled to tandem mass spectrometry was applied to obtain a comprehensive lipid profile for the simultaneous evaluation of phospholipids removal and diacylglycerol (DAG) increase. A significant increase for all the monitored DAG species, up to 138.42%, was observed by using the enzymatic degumming, in comparison to the crude sample, resulting in an increased oil yield. Serratia sp. W3 lipase was identified as a suitable biocatalyst for biodiesel production, converting efficiently the acylglycerols. The results regarding the physical-chemical characteristics show that the cetane level, density and pour point of the obtained biodiesel are close to current regulation requirements. These findings highlight the potential of a two-step process implementation, based on the combination of lipase and phospholipase, as a suitable alternative for biodiesel production.

Thermal Stabilization of a Bacterial Zn(II)-Dependent Phospholipase C through Consensus Sequence Design

Proteins' extraordinary performance in recognition and catalysis has led to their use in a range of applications. However, proteins obtained from natural sources are oftentimes not suitable for direct use in industrial or diagnostic setups. Natural proteins, evolved to optimally perform a task in physiological conditions, usually lack the stability required to be used in harsher conditions. Therefore, the alteration of the stability of proteins is commonly pursued in protein engineering studies. Here, we achieved a substantial thermal stabilization of a bacterial Zn(II)-dependent phospholipase C by consensus sequence design. We retrieved and analyzed sequenced homologues from different sources, selecting a subset of examples for expression and characterization. A non-natural consensus sequence showed the highest stability and activity among those tested. Comparison of the stability parameters of this stabilized mutant and other natural variants bearing similar mutations allows us to pinpoint the sites most likely to be responsible for the enhancement. Point mutations in these sites alter the unfolding process of the consensus sequence. We show that the stabilized version of the protein retains full activity even in harsh oil degumming conditions, making it suitable for industrial applications.