Constitutive secretory expression and characterization of nitrilase from Alcaligenes faecalis in Pichia pastoris for production of R-mandelic acid

Nitrilase GiNIT from Gibberella intermedia Efficiently Degrades Nitriles Derived from Rapeseed Meal Glucosinolate

Rapeseed meal is severely restricted in its utilization as unconventional animal feed due to anti-nutritive compounds, such as glucosinolate, that are degraded to toxic nitriles such as 3-butenenitrile and 4-pentenenitrile in animals. Few studies on nitrilases that can degrade glucosinolate-derived nitriles have been reported thus far. In the present study, a nitrilase gene GiNIT from Gibberella intermedia was over-expressed in Escherichia coli and the purified recombinant nitrilase rGiNIT showed specific activities of 134.48 U/mg and 122.16 U/mg when using 3-butenenitrile and 4-pentenenitrile as substrates at the optimal pH, 7.5, and temperature, 45 °C, which is the highest reported in the literature. The conversion of 3-butenenitrile and 4-pentenenitrile by rGiNIT reached 81.89% and 80.23% after hydrolysis for 15 min and 300 min, respectively. Site-directed mutagenesis and molecular docking analysis revealed that the catalytic ability of rGiNIT depended on the substrate binding pocket comprising 13 key amino acid residues. These results provide a potential enzyme resource for rapeseed meal detoxification and theoretical guidance for protein engineering.

Zinc and cadmium change the metabolic activities and vegetable cellulose degradation of Bacillus cellulasensis in vegetable soils

Bacillus cellulasensis Zn-B isolated from vegetable soil was highly adaptable to Zinc (Zn) and Cadmium (Cd). Cd, but not Zn, adversely affected the total protein spectrum and functional groups of Bacillus cellulasensis Zn-B. Up to 31 metabolic pathways and 216 metabolites of Bacillus cellulasensis Zn-B were significantly changed by Zn and Cd (Zn&Cd). Some metabolic pathways and metabolites related to functional groups of sulfhydryl (-SH) and amine (-NH-) metabolism were enhanced by Zn&Cd addition. The cellulase activity of Bacillus cellulasensis Zn-B was up to 8.58 U mL^-1, increased to 10.77 U mL^-1 in Bacillus cellulasensis Zn-B + 300 mg L^-1 Zn, and maintained at 6.13 U mL^-1 in Bacillus cellulasensis Zn-B + 50 mg L^-1 Cd. The vegetables' cellulose content was decreased by 25.05-52.37% and 40.28-70.70% under the action of Bacillus cellulasensis Zn-B and Bacillus cellulasensis Zn-B + 300 mg L^-1 Zn. Those results demonstrated that Zn could significantly enhance cellulase activity and biodegradability of Bacillus cellulasensis Zn-B to vegetable cellulose. Bacillus cellulasensis Zn-B can survive in vegetable soil accumulated with Zn&Cd. The tolerance concentration and adsorption capacity of Bacillus cellulasensis Zn-B to Zn were up to 300 mg L^-1 and 56.85%, indicating that Bacillus cellulasensis Zn-B acting as a thermostability biological agent had an essential advantage in accelerating the degradation of discarded vegetables by Zn and were beneficial to maintain organic matter content of vegetable soil.

Recent Progress in the Production of Cyanide-Converting Nitrilases—Comparison with Nitrile-Hydrolyzing Enzymes

Nitrilases have a high potential for application in organic chemistry, environmental technology, and analytics. However, their industrial uses require that they are produced in highly active and robust forms at a reasonable cost. Some organic syntheses catalyzed by nitrilases have already reached a high level of technological readiness. This has been enabled by the large-scale production of recombinant catalysts. Despite some promising small-scale methods being proposed, the production of cyanide-converting nitrilases (cyanide hydratase and cyanide dihydratase) is lagging in this regard. This review focuses on the prospects of cyanide(di)hydratase-based catalysts. The current knowledge of these enzymes is summarized and discussed in terms of the origin and distribution of their sequences, gene expression, structure, assays, purification, immobilization, and uses. Progresses in the production of other nitrilase catalysts are also tackled, as it may inspire the development of the preparation processes of cyanide(di)hydratases.

Potential of the Signal Peptide Derived from the PAS_chr3_0030 Gene Product for Secretory Expression of Valuable Enzymes in Pichia pastoris

Pichia pastoris is widely used for the production of valuable recombinant proteins. An advantage of P. pastoris over other expression systems is that it secretes low levels of endogenous proteins, which facilitates the purification processes if the desired recombinant proteins are efficiently secreted into the culture medium. However, not all recombinant proteins can be successfully secreted by P. pastoris, especially enzymes that are located in intracellular compartments in their native hosts. Few studies have reported strategies for releasing recombinant proteins which cannot be secreted by standard protocols. Here, we investigated whether this challenge can be addressed using novel secretion leaders. Analysis of the secretome and transcriptome of P. pastoris indicated that the four genes with the highest protein-to-transcript ratios were EPX1, PAS_chr3_0030, SCW10, and UTH1, suggesting that their gene products contain efficient secretion leaders. Our data revealed that the signal peptide derived from the PAS_chr3_0030 gene product conferred secretion competence to certain industrial enzymes, e.g., a nitrilase of Alcaligenes faecalis ZJUTB10, a ribosylnicotinamide kinase of P. pastoris, and a glucose dehydrogenase of Exiguobacterium sibiricum. Therefore, the signal peptide derived from the PAS_chr3_0030 gene product represents a novel secretion sequence for the secretory expression of recombinant enzymes in P. pastoris. IMPORTANCE Although P. pastoris is widely used for the secretory production of pharmaceutical proteins, its successful applications in the secretory production of industrial enzymes are limited. The α-mating factor pre-pro leader is the most widely used secretion signal in P. pastoris, but numerous industrial enzymes cannot be secreted using it. The importance of this study is that we identified a signal peptide derived from the PAS_chr3_0030 gene product which conferred secretion competence to three-quarters of the enzymes tested. This signal peptide derived from the PAS_chr3_0030 gene product may facilitate the application of P. pastoris in industrial biocatalysis.