Optimization of the degumming process for camellia oil by the use of phospholipase C in pilot-scale system

Enhancing the Thermostability of Phospholipase C by Structural-Based Proline Incorporation to Improve Its Degumming Performance

Thermostability can be improved by introducing prolines into targeted sites, enhancing enzyme performance in specific reactions. In our present study, a novel fungal phospholipase C derived from Talaromyces islandicus (TiPLC) was first heterologously expressed in Pichia pastoris and biochemically characterized. Given the poor thermal stability of TiPLC, a structure-based proline incorporation strategy was used to enhance its thermostability further. Two single-site (E92P and A375P) mutants were selected from seven designs, exhibiting improved stability while retaining wild-type's basic properties (optimum reaction pH and temperature). Compared to the wild-type, the t1/2 of E92P and A375P under 40 °C extended by 1.62 and 1.27 times, respectively. Meanwhile, the E92P and A375P mutants exhibited a 20% increase in activity using p-NPPC as substrate. Moreover, double mutant E92P-A375P exhibited 2.43 times enhancement compared to the wild-type. Results of the oil degumming experiment further confirmed that the double mutant significantly improved the performance of TiPLC, with a reduction in residual phosphorus to 78 ppm, while for the wild-type, the residual phosphorus was 131 ppm under the same reaction. Molecular simulations indicated that proline incorporation into 92 and 375 sites significantly improved the rigidity of partial flexible regions, thus contributing to the increased thermostability.

Fatty acid composition, bioactive phytochemicals, antioxidant properties and oxidative stability of edible fruit seed oil: effect of preharvest and processing factors

Fruit seed is a by-product of fruit processing into juice and other products. Despite being treated as waste, fruit seed contains oil with health benefits comparable or even higher than the conventional seed oil from field crops. In addition to essential fatty acids, the fruit seed oil is a rich source of bioactive compounds such as tocopherols, carotenoids, flavonoids, phenolic acids and phytosterols, which have been implicated in the prevention of chronic and degenerative diseases such as cancer, diabetes and cardiovascular diseases. The emerging potential of fruit seed oil application in food and nutraceuticals has prompted researchers to study the effect of preharvest and processing factors on the seed oil quality with respect to nutritional qualities, antioxidant compounds and properties. Herein, the effect of cultivar, fruit-growing region, seeds pretreatment, seeds drying and seed oil extraction on tocopherols, polyphenols, phytosterols, carotenoids, fatty acids, antioxidant activity and oxidative stability of the fruit seed oil is critically discussed. Understanding the influence of these factors on seed oil bioactive phytochemicals, nutritional qualities and antioxidant properties is critical not only for genetically improving the oilseeds plants with desired characteristics, but also in seed oil processing and value addition. Therefore, preharvest and processing factors are essential considerations when determining the application of fruit seed oil.

CopySwitch-in vivo Optimization of Gene Copy Numbers for Heterologous Gene Expression in Bacillus subtilis

The Gram-positive bacterium Bacillus subtilis has long been used as a host for production and secretion of industrially relevant enzymes like amylases and proteases. It is imperative for optimal efficiency, to balance protein yield and correct folding. While there are numerous ways of doing so on protein or mRNA level, our approach aims for the underlying number of coding sequences. Gene copy numbers are an important tuning valve for the optimization of heterologous gene expression. While some genes are best expressed from many gene copies, for other genes, medium or even single copy numbers are the only way to avoid formation of inclusion bodies, toxic gene dosage effects or achieve desired levels for metabolic engineering. In order to provide a simple and robust method to address above-mentioned issues in the Gram-positive bacterium Bacillus subtilis, we have developed an automatable system for the tuning of heterologous gene expression based on the host's intrinsic natural competence and homologous recombination capabilities. Strains are transformed with a linearized, low copy number plasmid containing an antibiotic resistance marker and homology regions up- and downstream of the gene of interest. Said gene is copied onto the vector, rendering it circular and replicative and thus selectable. We could show an up to 3.6-fold higher gfp (green fluorescent protein) expression and up to 1.3-fold higher mPLC (mature phospholipase C) expression after successful transformation. Furthermore, the plasmid-borne gfp expression seems to be more stable, since over the whole cultivation period the share of fluorescent cells compared to all measured cells is consistently higher. A major benefit of this method is the ability to work with very large regions of interest, since all relevant steps are carried out in vivo and are thus far less prone to mechanical DNA damage.

Multi-walled carbon nanotubes act as a chemokine and recruit macrophages by activating the PLC/IP3/CRAC channel signaling pathway

The impact of nanomaterials on immune cells is gaining attention but is not well documented. Here, we report a novel stimulating effect of carboxylated multi-walled carbon nanotubes (c-MWCNTs) on the migration of macrophages and uncover the underlying mechanisms, especially the upstream signaling, using a series of techniques including transwell migration assay, patch clamp, ELISA and confocal microscopy. c-MWCNTs dramatically stimulated the migration of RAW264.7 macrophages when endocytosed, and this effect was abolished by inhibiting phospholipase C (PLC) with U-73122, antagonizing the IP3 receptor with 2-APB, and blocking calcium release-activated calcium (CRAC) channels with SK&F96365. c-MWCNTs directly activated PLC and increased the IP3 level and [Ca²⁺]_i level in RAW264.7 cells, promoted the translocation of the ER-resident stromal interaction molecule 1 (STIM1) towards the membranous calcium release-activated calcium channel modulator 1 (Orai1), and increased CRAC current densities in both RAW264.7 cells and HEK293 cells stably expressing the CRAC channel subunits Orai1 and STIM1. c-MWCNTs also induced dramatic spatial polarization of KCa3.1 channels in the RAW264.7 cells. We conclude that c-MWCNT is an activator of PLC and strongly recruits macrophages via the PLC/IP3/CRAC channel signaling cascade. These novel findings may provide a fundamental basis for the impact of MWCNTs on the immune system.