Characterization of a novel thermostable phospholipase C from T. kodakarensis suitable for oil degumming

The implementation of cleaner technologies that minimize environmental pollution caused by conventional industrial processes is an increasing global trend. Hence, traditionally used chemicals have been replaced by novel enzymatic alternatives in a wide variety of industrial-scale processes. Enzymatic oil degumming, the first step of the oil refining process, exploits the conversion catalyzed by phospholipases to remove vegetable crude oils' phospholipids. This enzymatic method reduces the gums' volume and increases the overall oil yield. A thermostable phospholipase would be highly advantageous for industrial oil degumming as oil treatment at higher temperatures would save energy and increase the recovery of oil by facilitating the mixing and gums removal. A thermostable phosphatidylcholine (PC) (and phosphatidylethanolamine (PE))-specific phospholipase C from Thermococcus kodakarensis (TkPLC) was studied and completely removed PC and PE from crude soybean oil at 80 °C. Due to these characteristics, TkPLC is an interesting promising candidate for industrial-scale enzymatic oil degumming at high temperatures. KEY POINTS: • A thermostable phospholipase C from T. kodakarensis (TkPLC) has been identified. • TkPLC was recombinantly produced in Pichia pastoris and successfully purified. • TkPLC completely hydrolyzed PC and PE in soybean oil degumming assays at 80 °C.

Industrial uses of phospholipases: current state and future applications

Phospholipids play a central role in all living organisms. Phospholipases, the enzymes aimed at modifying phospholipids, are consequently widespread in nature and play diverse roles, from lipid metabolism and cellular signaling in eukaryotes to virulence and nutrient acquisition in microbes. Phospholipases catalyze the hydrolysis of one or more ester or phosphodiester bonds of glycerophospholipids. The use of phospholipases with industrial purposes has constantly increased over the last 30 years. This demand is rapidly growing given the ongoing improvements in protein engineering and the reduction of enzymes manufacturing costs, making them suitable for industrial use. Here, a general overview of phopholipases A, B, C, and D and their industrial application is presented along with potential new uses for these enzymes. We draw attention to commercial phospholipases used to improve the emulsifying properties of products in the baking, egg, and dairy industries. On the other hand, the improvement of oil degumming by phospholipases is thoroughly analyzed. Moreover, recent developments in enzymatic biodiesel production and the use of phospholipases for the synthesis of phospholipids with pharmaceutical or nutritional value are reviewed.

The CpxR/CpxA system contributes to Salmonella gold-resistance by controlling the GolS-dependent gesABC transcription

Several regulatory systems contribute to bacterial resistance to heavy metals controlling the expression of factors required to eliminate the intoxicant and/or to repair the damage caused by it. In Salmonella, the response to Au ions is mediated by the specific metalloregulator GolS that, among other genes, controls the expression of the RND-efflux pump GesABC. In this work, we demonstrate that CpxR/CpxA, a main cell-envelope stress-responding system, promotes gesABC transcription in the presence of Au ions at neutral pH. Deletion of either cpxA or cpxR, or mutation of the CpxR-binding site identified upstream of the GolS-operator in the gesABC promoter region reduces but does not abrogate the GolS- and Au-dependent activation of gesABC. Au also triggers the activation of the CpxR/CpxA system and deletion of the cpxRA operon severely reduces survival in the presence of the toxic metal. Our results indicate that the coordinated action of GolS and CpxR/CpxA contribute to protecting the cell from severe Au damage.

Development of a highly efficient oil degumming process using a novel phosphatidylinositol-specific phospholipase C enzyme

Enzymatic degumming using phospholipase C (PLC) enzymes may be used in environmentally friendly processes with improved oil recovery yields. In this work, phosphatidylinositol-specific phospholipase C (PIPLC) candidates obtained from an in silico analysis were evaluated for oil degumming. A PIPLC from Lysinibacillus sphaericus was shown to efficiently remove phosphatidylinositol from crude oil, and when combined with a second phosphatidylcholine and phosphatidylethanolamine-specific phospholipase C, the three major phospholipids were completely hydrolyzed, providing an extra yield of oil greater than 2.1%, compared to standard methods. A remarkably efficient fed-batch Escherichia coli fermentation process producing ∼14 g/L of the recombinant PIPLC enzyme was developed, which may facilitate the adoption of this cost-effective oil-refining process.

A sensitive whole-cell biosensor for the simultaneous detection of a broad-spectrum of toxic heavy metal ions

Bacterial biosensors are simple, cost-effective and efficient analytical tools for detecting bioavailable heavy metals in the environment. This work presents the design, construction and calibration of a novel whole-cell fluorescent biosensory device that, simultaneously and with high sensitivity, reports the presence of toxic mercury, lead, cadmium and/or gold ions in aqueous samples. This bio-reporter can be easily applied as an immediate alerting tool for detecting the presence of harmful pollutants in drinking water.