Genomic and transcriptomic analysis of Bacillus subtilis JNFE1126 with higher nattokinase production through ultraviolet combined 60Co-γ ray mutagenesis

Phenotypic and genomic insights into mutant with high nattokinase-producing activity induced by carbon ion beam irradiation of Bacillus subtilis

Nattokinase (NK) is found in fermented foods and has high fibrinolytic activity, which makes it promising for biological applications. In this study, a mutant strain (Bacillus subtilis ZT-S1, 5529.56 ± 183.59 U/mL) with high NK-producing activity was obtained using 12C6+ heavy ion beam mutagenesis for the first time. The surface morphology of B. subtilis is also altered by changes in functional groups caused by heavy ion beams. Furthermore, B. subtilis ZT-S1 required more carbon and nitrogen sources and reached stabilization phase later. Comparative genome analysis revealed that most of the mutant implicated genes (oppA, appA, kinA, spoIIP) were related to spore formation. And the affected rpoA is related to the synthesis of the NK-coding gene aprE. In addition, the B. subtilis ZT-S1 obtained by mutagenesis had good genetic stability. This study further explores the factors affecting NK activity and provides a promising microbial resource for NK production in commercial applications.

Nitrogen removal by Rhodococcus sp. SY24 under linear alkylbenzene sulphonate stress: Carbon source metabolism activity, kinetics, and optimum culture conditions

Artificial intervention combined with stress acclimation was used to screen a heterotrophic nitrifying-aerobic denitrifying (HN-AD) bacterial, strain Rhodococcus SY24, resistant to linear alkylbenzenesulfonic acid (LAS) stress. When LAS was<15 mg/L, strain SY24 performed better cell growth and carbon source metabolism activity. The maximum nitrification and denitrification rates of SY24 under LAS stress could reach 1.18 mg/L/h and 1.05 mg/L/h, respectively, which were 13.80 % and 8.81 % higher than those of the original strain CPZ24. Higher LAS tolerance was seen in the functional genes (amoA, nxrA, napA, narG, nirK, nirS, norB, and nosZ). Response surface modeling revealed that 2 mg/L LAS, sodium succinate as a carbon source, 190 rams, and carbon/nitrogen 11 were the ideal culture conditions for SY24 to nitrogen removal under the LAS environment. This study offered a new screening strategy for the functional species, and strain SY24 showed significant LAS tolerance and HN-AD potential.

Identification of Novel Bile Salt-Tolerant Genes in Lactobacillus Using Comparative Genomics and Its Application in the Rapid Screening of Tolerant Strains

Under bile salt treatment, strains display significant differences in their tolerance ability, suggesting the existence of diverse resistance mechanisms in Lactobacillus; however, the genes involved in this protective process are not fully understood. In this study, novel target genes associated with bile salt tolerance in Lactobacillus were identified using comparative genomics for PCR detection and the rapid screening of tolerant strains. The bile salt tolerance of 107 lactobacilli isolated from different origins was assessed, and 26 strains with comparatively large differences were selected for further comparative genomic analysis. Tolerant strains had 112 specific genes that were enriched in the phosphotransferase system, the two-component system, carbohydrate metabolism, and the ATP-binding cassette transporter. Six genes from Lactobacillus were cloned into the inducible lactobacillal expression vector pSIP403. Overexpression in the host strain increased its tolerance ability by 11.86-18.08%. The novel genes identified here can be used as targets to design primers for the rapid screening of bile salt-tolerant lactobacilli. Altogether, these results deepen our understanding of bile salt tolerance mechanisms in Lactobacillus and provide a basis for further rapid assessments of tolerant strains.

Mutagenesis of high-efficiency heterotrophic nitrifying-aerobic denitrifying bacterium Rhodococcus sp. strain CPZ 24

Breeding high-efficiency heterotrophic nitrifying-aerobic denitrifying (SND) bacteria is important for the removal of biological nitrogen in wastewater treatment. In this study, a high-efficiency SND mutant strain, ΔRhodococcus sp. CPZ 24, was obtained by ultraviolet-diethyl sulfate compound mutagenesis. The maximum nitrification and denitrification rates were 3.77 and 1.37 mg·L^-1·h^-1, respectively 30.30 % and 17.10 % higher than those of wild bacteria. Biolog technology and network model analysis revealed that ΔCPZ 24 significantly improved the utilisation ability and metabolic activity of organic carbon sources. Furthermore, the expression levels of the nitrogen removal function genes nxrA, nosZ, amoA, and norB in strain ΔCPZ 24 increased significantly. In actual sewage, mutant bacteria ΔCPZ 24 have a 95.05 % ammonia-nitrogen degradation rate and a 96.67 % nitrate-nitrogen degradation rate. These results suggested that UV-DES compound mutation was a successful strategy to improve the nitrogen removal performance of SND bacteria in wastewater treatment.

Molecular mechanism of high-production tannase of Aspergillus carbonarius NCUF M8 after ARTP mutagenesis: revealed by RNA-seq and molecular docking

BACKGROUND

Tannase is an enzyme produced by microbial fermentation and is widely used in the food industry; however, the molecular mechanism of tannase production by Aspergillus has not yet been studied. This study was conducted to reveal the differences in Aspergillus carbonarius tannase enzymatic characterization, secondary structures and molecular mechanisms after treatment of the strain with atmospheric and room temperature plasma (ARTP).

RESULTS

The results showed that the specific activity of tannase was improved by ARTP treatment, and it showed higher thermostability and tolerance to metal ions and additives. The enzymatic characterization and molecular docking results indicated that tannase had a higher affinity and catalytic rate with tannic acid as a substrate after ARTP treatment. In addition, the docking results indicated that Aspergillus tannases may catalyze tannic acid by forming two hydrogen-bonding networks with neighboring residues. RNA-seq analysis indicated that changes in steroid biosynthesis, glutathione metabolism, glycerolipid metabolism, oxidative phosphorylation pathway and mitogen-activated protein kinase signaling pathways might be crucial reasons for the high production of tannase.

CONCLUSION

ARTP enhanced the yield and properties of A. carbonarius tannase by changing the enzyme structure and cell metabolism. This study provides a theoretical basis for elucidating the molecular mechanism underlying high production of Aspergillus tannases. © 2022 Society of Chemical Industry.