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Due to the increasing demand for green processes in renewable energy production, the extracellular Bacillus subtilis B-1-4 lipase was used as a biocatalyst for producing biodiesel from waste cooking oil. Response surface methodology was employed for the optimization of enzyme production. Lipase activity was modeled with a quadratic function of four factors that primarily influence the culture medium. Thanks to this model, an optimal lipase activity of 1.7 ± 0.082 U/mL was achieved with the best culture medium composition: 16 g/L of tryptone, 15 g/L of yeast extract, 15 g/L of NaCl, and a 0.15 initial optical density at 600 nm (OD600 nm). The maximal lipase activity was measured at 45 °C and pH 8, using para-nitrophenyl palmitate as a substrate. The enzyme maintained above 94% and 99% of its initial activity at temperatures ranging from 40 to 50 °C and at pH 8, respectively. Moreover, it exhibited a higher residual activity than other Bacillus lipases in the presence of organic solvents. Residual activities of 86.7% and 90.2% were measured in the presence of isopropanol and ethanol, respectively. The lipase was immobilized by adsorption onto CaCO3 powder. FT-IR and SEM were used to characterize the surface-modified support. After immobilization, a lipase activity of 7.1 U/mg of CaCO3 was obtained. Under the optimized conditions, the highest biodiesel yield of 71% was obtained through the transesterification of waste cooking oil using the CaCO3-immobilized Bacillus subtilis lipase. This research reveals a method for the utilization of waste cooking oil for biodiesel production using an efficient immobilized thermostable lipase, providing environmental and economic security. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An immobilized enzyme could exhibit selectively modified physicochemical properties, and it might offer a better environment for the enzyme activity. In this study, the immobilization yield of crude Halomonas sp. lipase was optimized to improve its stability. Thanks to its high adsorption capacity, CaCO3 has been chosen as support for the immobilization process. Furthermore, response surface methodology (RSM) was used to determine optimal conditions for the immobilization of the bacterial lipase. Five tested factors (enzyme solution, support amount, time, temperature, and acetone volume) were optimized applying a central composite design of RSM. The maximum yield of lipase immobilization was improved to 96%. Furthermore, a biochemical characterization proved a significant improvement of the immobilized lipase stability. The immobilized enzyme is more stable at extreme pH values and high temperatures than the free one. We also tested the reusability of the immobilized lipase by evaluating the recovery of the support using simple filtration. Thanks to its high stability, the immobilized lipase was invested in an effective treatment of tuna wash processing wastewater. The oil biodegradation efficiency was established at 81.5% and was confirmed by Fourier transformation infrared spectrometry. Likewise, the biological oxygen demand values were reduced which makes a possible reduction of the wastewater pollution degree. [ABSTRACT FROM AUTHOR]

The aim of this work was to optimize the production of a new lipase by a halotolerant bacterial strain Halomonas sp. C2SS100, by means of the response‐surface methodology (RSM). The process parameters having the most significant effect on lipase production were identified using the Plackett–Burman screening design‐of‐experiments. Then, Box–Behnken design was applied to optimize lipase activity and the quadratic regression model of the lipase production was built. Indeed, the lipase yield was increased, and the value obtained experimentally (39 ± 2 U/ml) was very close to the rate predicted by the model (40.3 U/ml). Likewise, optimization of parameters by RSM resulted in 2.78‐fold increase in lipase activity. These findings provide the first report on lipase production and optimization by a halotolerant bacterial strain belonging to Halomonas genus. Afterward, the biochemical properties of the produced lipase were studied for apply in oil stains removal. The crude lipase showed a maximum activity at 60°C and at pH ranging from 7 to 10. It displayed an important stability at high temperature, pH, and NaCl. Interestingly, this bacterial lipase exhibited a prominent stability toward some commercial solid and liquid detergents after 30 min of incubation at 50°C. The capability of the crude lipase to eliminate stain was ascertained on polycotton fabric pieces stained with lubricating oil. Whether with the addition of hot water alone or of a commercially available detergent, lipase is able to considerably boost the elimination of oil stains. The actual findings highlight the capacity of Halomonas sp. lipase for energy‐efficient biocatalytic application. [ABSTRACT FROM AUTHOR]