Various Strategies for the Immobilization of a Phospholipase C from Bacillus cereus for the Modulation of Its Biochemical Properties

In this study, the effect of various immobilization methods on the biochemical properties of phospholipase C (PLC) from Bacillus cereus obtained from the oily soil located in Sfax, Tunisia, was described. Different supports were checked: octyl sepharose, glyoxyl agarose in the presence of N-acetyl cysteine, and Q-sepharose. In the immobilization by hydrophobic adsorption, a hyperactivation of the PLCBc was obtained with a fold of around 2 times. The recovery activity after immobilization on Q-sepharose and glyoxyl agarose in the presence of N-acetyl cysteine was 80% and 58%, respectively. Furthermore, the biochemical characterization showed an important improvement in the three immobilized enzymes. The performance of the various immobilized PLCBc was compared with the soluble enzyme. The derivatives acquired using Q-sepharose, octyl sepharose, and glyoxyl agarose were stable at 50 °C, 60 °C, and 70 °C. Nevertheless, the three derivatives were more stable in a large range of pH than the soluble enzyme. The three derivatives and the free enzyme were stable in 50% (v/v) ethanol, hexane, methanol, and acetone. The glyoxyl agarose derivative showed high long-term storage at 4 °C, with an activity of 60% after 19 days. These results suggest the sustainable biotechnological application of the developed immobilized enzyme.

Optimization using response surface methodology of phospholipase C production from Bacillus cereus suitable for soybean oil degumming

This work deals with the optimization of an extracellular phospholipase C production by Bacillus cereus (PLCBc) using Response Surface Methodology (RMS) and Box-Behnken design. In fact, after optimization, a maximum phospholipase activity (51 U/ml) was obtained after 6 h of cultivation on tryptone (10 g/L), yeast extract (10 g/L), NaCl (8.125 g/L), pH 7.5 with initial OD (0.15). The PLCBc activity, esteemed by the model (51 U) was very approximate to activity gutted experimentally (50 U). The PLCBc can be considered as thermoactive phospholipase since it showed a maximal activity of 50 U/mL at 60 °C using egg yolk or egg phosphatidylcholine (PC) as substrate. In addition, the enzyme was active at pH 7 and is stable after incubation at 55 °C for 30 min. The application of B. cereus phospholipase C in soybean oil degumming was investigated. Our results showed that when using enzymatic degumming, the residual phosphorus decrease more than with water degumming, indeed, it passes from 718 ppm in soybean crude oil to 100 ppm and 52 ppm by degumming using water and enzymatic process, respectively. The diacylgycerol (DAG) yield showed an increase of 1.2% with enzymatic degumming compared to soybean crude oil. This makes our enzyme a potential candidate for food industrial applications such as enzymatic degumming of vegetable oils.

Efficient production of a novel alkaline cold-active phospholipase C from Aspergillus oryzae by molecular chaperon co-expression for crude oil degumming

A novel alkaline cold-active phospholipase C (PLC) gene (AoPC) from Aspergillus oryzae was cloned. AoPC exhibited the highest sequence similarity of 32.5% with that of a PLC from Arabidopsis thaliana. The gene was co-expressed in Pichia pastoris with molecular chaperone PDI (protein disulfide isomerases), and the highest PLC activity of 82, 782 U mL^-1 was achieved in a 5-L fermentor. The recombinant enzyme (AoPC) was most active at pH 8.0 and 25 °C, respectively, and it was stable over a broad pH range of 4.5-9.0 and up to 40 °C. It is the first fungal alkaline PLC. The application of AoPC (with 25% citric acid, w/w) in oil degumming process significantly reduced the phosphorus of crude soybean oil by 93.3% to a commercially acceptable level (<10 mg kg^-1). Therefore, the relatively high yield and excellent properties of AoPC may possess it great potential in crude oil refining industry.

Effective Expression of the Serratia marcescens Phospholipase A1 Gene in Escherichia coli BL21(DE3), Enzyme Characterization, and Crude Rapeseed Oil Degumming via a Free Enzyme Approach

Crude oil degumming by phospholipid removal is crucial to guarantee oil quality. Phospholipase degumming could produce green vegetable oil by reducing energy consumption and protecting the environment. To develop a novel phospholipase for oil degumming, we cloned the Serratia marcescens outer membrane phospholipase A gene (OM-PLA1) and expressed its 33 KDa protein in engineered Escherichia coli BL21(DE3). OM-PLA1 activity reached 18.9 U mL^-1 with the induction of 0.6 mM isopropyl β-D-1-thiogalactopyranoside for 4 h. The optimum temperature and pH were 50°C and 7.5, respectively. Mg²⁺, Ca²⁺, Co²⁺, and Mn²⁺ at 0.1 mM L^-1 significantly increased OM-PLA1 activity. The kinetic equations of OM-PLA1 and Lecitase Ultra were y = 13.7x+0.74 (K_m = 18.53 mM, V_max = 1.35 mM min^-1) and y = 24.42x+0.58 (K_m = 42.1 mM, V_max = 1.72 mM min^-1), respectively. The phosphorus content decreased from 22.6 to 9.3 mg kg^-1 with the addition of 15 units of free recombinant OM-PLA1 into 150 g of crude rapeseed oil. OM-PLA1 has the close degumming efficiency with Lecitase Ultra. The S. marcescens outer membrane phospholipase gene (OM-PLA1) possessed higher substrate affinity and catalytic efficiency than Lecitase Ultra. This study provides an alternative approach to achieve crude vegetable oil degumming with enzymatic technology.