JOURNAL OF BIOSCIENCE AND BIOENGINEERING
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2019
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IF 2.032
Xiaohong Lu,Juhua Chen,Linshu Jiao,Lei Zhong,Zhaoxin Lu,Chong Zhang,Fengxia Lu
Directed evolution methodologies have been used as promising strategies for improving the catalytic properties of many existing enzymes . In the presented work, this approach was applied to improve the enzyme activity of l -asparaginase I obtained from Bacillus megaterium H-1. After two rounds of error-prone polymerase chain reaction (epPCR) and two generations of sequential DNA shuffling , all of 5 different mutants showed a significant increase in the enzyme activity of l -asparaginase I, ranging from 6.27 to 22.78 IU/mL. Among these mutants, D-9B and DD-12G displayed the relatively high catalytic activity , which were 20.22-fold and 21.33-fold higher than the wild-type enzyme (WT), respectively. Furthermore, the catalytic efficiency ( k cat / K m ) of D-9B and DD-12G were also improved, which were 132.73 min −1 mM −1 and 146.39 min −1 mM −1 , respectively, in comparison to that of WT (3.39 min −1 mM −1 ). In addition, mutant DD-12G showed tolerance toward wider range of pH values and higher temperatures than its WT counterpart. Homology modeling of above two mutants reflected a reduction of hydrogen bonds and an introduction of flexible residues in the loops near the active catalytic site Thr15. These changes contributed to the flexibility of loops, which may lead to further enhancement in catalytic efficiency. Results also showed that approximately 88.5% (0.978 mg/kg) acrylamide could be removed from mutant DD-12G pre-treated fried potato chips. This study clearly shows that directional evolution methods can indeed be utilized to improve the activity of l -asparaginase, which could also provide research basis for future application in food industry.
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Journal of Environmental Chemical Engineering
·
2025
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IF 7.2
Yating Jia,Jing Lu,Yongfen Long,Bin Hou,Yuancai Chen
Microbially synthesized palladium nanoparticles (bio-Pd 0 ) hold great promise for catalysis, but the catalytic activity of bio-Pd 0 relies heavily on its subcellular localization. Electron donors could affect enzymatic reduction efficiency of Pd(II) and control the subcellular location of bio-Pd 0 , yet the underlying mechanisms were unclear. Here, the regulatory mechanism of electron donors on Pd(II) reduction pathways in the non-model bacterium B. megaterium Y-4 was comprehensively investigated by multiple methodologies including cell fractionation, DPV/CV, XPS, FTIR, TEM, proteomics. Key findings revealed that membrane-bound hydrogenases drove periplasmic Pd 0 synthesis via biohydrogen, while the new one-electron extracellular transfer (EET) channel consisting of membrane-attached cytochromes ( ccsB ) and multi-heme cytochromes-bound flavin mediated the extracellular Pd(II) reduction. Notably, electron donors could regulate Pd(II) reduction routes, thereby altering the subcellular distribution of bio-Pd 0 . In lactate-added systems, the higher expression of these proteins related to EET processes (NADH dehydrogenase, membrane-attached cytochrome c, heme-based electron transfer proteins and flavodoxin) promoted extracellular Pd 0 formation (65.4 %). Whereas, in formate-added systems, hydrogenase-driven periplasmic Pd 0 synthesis (64.0 %) was facilitated due to more active formate dehydrogenase, hydrogenase and NADPH-reducing hydrogenase. Moreover, synergistical metabolism of formate and lactate balanced both pathways and maximized the apparent Pd(II) reduction efficiency (98.13 %). Proteomic analysis confirmed formate-specific energy rewiring and compensatory energy via Na⁺-translocating Rnf complex and V-ATPase overexpression. These findings significantly advance our understanding of microbial metal reduction by delineating a true dual-pathway strategy in a Gram-positive bacterium, highlighting the mechanistic diversity beyond model Gram-negative systems and offering new insights for harnessing non-model organisms in biocatalysis and nanoparticle synthesis.
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BIOORGANIC CHEMISTRY
·
2022
·
IF 5.307
Hongjun Zhang,Zeguang Cheng,Litian Wei,Xinjun Yu,Zhao Wang,Yinjun Zhang
A gene encoding an esterase from Bacillus aryabhattai (BaCE) was identified, synthesized and efficiently expressed in the Escherichia coli system. A semi-rational protein engineering was applied to further improve the enzyme’s enantioselectivity. Under the guidance of the molecular docking result, a single mutant BaCE-L86Q and a double mutant BaCE-L86Q/G284E were obtained, with its E max value 6.4 times and 13.9 times of the wild-type BaCE, respectively. The recombinant BaCEs were purified and characterized. The overwhelming E value demonstrated that BaCE-L86Q/G284E was a promising biocatalyst for the biological resolution to prepare ( S )-indoline-2-carboxylic acid.
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ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY
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2020
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IF 4.872
You-Wei Xiong,Xue-Wei Li,Tian-Tian Wang,Yuan Gong,Chun-Mei Zhang,Ke Xing,Sheng Qin
Halophytes play an important role in the bioremediation of saline soils . Increased evidence has revealed that plant growth-promoting rhizobacteria (PGPR) have colonized the halophytic rhizosphere, and they have evolved the capacity to reduce salt stress damage to the host. However, the mechanism by which halophytes attract and recruit beneficial PGPR has rarely been reported. This study reports the interaction between the halophyte Limonium sinense and its rhizosphere PGPR strain Bacillus flexus KLBMP 4941, as well as the mechanism by which KLBMP 4941 promotes host plant growth under salt stress. After salt stress treatment, we collected the root exudates (REs) of L. sinense and found that the REs could promote the growth and chemotaxis of the bacterium KLBMP 4941. In addition, the components of the REs under salt stress were analyzed, and some organic acids ( 2-methylbutyric acid , stearic acid , palmitic acid , palmitoleic acid, and oleic acid) were detected as the major components. Further assessment showed that each of these components had positive effects on the growth, motility, chemotaxis, and root colonization of strain KLBMP 4941. Further pot experiments revealed the potential PGP mechanisms induced by strain KLBMP 4941 on the host plant under salt stress. Inoculation with KLBMP 4941 promoted the accumulation of chlorophyll to enhance photosynthesis, increased osmotic regulator contents, enhanced flavonoid and antioxidant enzymes, and regulated Na + /K + homeostasis to help the host ameliorate salinity stress damage. Our findings indicate that the halophyte L. sinense can attract and recruit beneficial rhizosphere bacteria by REs under salt stress, and the recruited B. flexus KLBMP 4941 elicited PGP effects under salinity stress through complex plant physiological regulatory mechanisms. This study provides a foundation for the enhancement of the rhizosphere colonization ability of the PGP strain KLBMP 4941, which shows potential applications in phytoremediation of saline soils.
研究领域:
植物学
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微生物学
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环境科学
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BIORESOURCE TECHNOLOGY
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2024
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IF 9.7
Yuxin Liu,Zhichao Kang,Quanying Wang,Tianye Wang,Ningning Song,Hongwen Yu
Microbial immobilization technology is effective in improving bioremediation efficiency and heavy metal pollution. Herein, Bacillus LD513 with hexavalent chromium (Cr(VI)) tolerance was isolated and immobilized on a novel ferrous disulfide (FeS 2 )/iron nitride (FeN) modified hydrochar (Fe3-SNHC) prepared from waste straws. The prepared Fe3-SNHC-based LD513 (FeLD) significantly improves Cr(VI) adsorption and reduction by 31.4 % and 15.7 %, respectively, compared to LD513 alone. Furthermore, the FeLD composite system demonstrates efficient Cr(VI) removal efficiency and good environmental adaptability under different culture conditions. Microbial metabolism and electrochemical analysis indicate that Fe3-SNHC is an ideal carrier for protecting LD513 activity, promoting extracellular polymer secretion, and reducing oxidative stress . Additionally, the carrier serves as an electron shuttle that accelerates electron transfer and promotes Cr(VI) reduction. Overall, FeLD is an environmentally friendly biocomposite that shows good promise for reducing Cr(VI) contamination in wastewater treatment.
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RSC Advances
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2025
·Vol. 15
·期 30
·24437
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IF 4.6
Feng Wen,Yongjun Wu,Jing Jin,Lincheng Zhang,Shuoqiu Tong,Cen Li,Li Ran,Yuzhang Zhu
Fermented soybean products are an integral part of the Chinese diet, valued for their distinctive aroma. Bacillus subtilis ( B. subtilis ) BJ3-2 is a highly effective fermentation strain widely used in the industrial production of bacterial-type douchi. However, the specific aroma characteristics of soybeans fermented by this strain remain unclear. This study utilized gene knockout, GC-O-MS, and multivariate statistical analysis to comprehensively investigate the aroma components of soybeans fermented by B. subtilis BJ3-2. For the first time, 12 key aroma skeleton compounds were identified, including guaiacol, 2,5-dimethylpyrazine, and 2-methylbutyric acid, which primarily contribute to the smoky, roasted, and sweaty aroma attributes of fermented soybeans. Additionally, 17 compounds were considered to have important coordinating effects on soybean aroma, such as 3-hydroxy-2-butanone (buttery, creamy). Partial least squares regression (PLSR) analysis demonstrated a good correlation between key aroma compounds and sensory attributes. Gene knockout of fadA and bkdB resulted in a significant increase in 2,5-dimethylpyrazine and 1-octen-3-ol levels, along with a marked reduction in 2-methylbutyric acid levels. These changes enhanced the roasted and beany notes, reduced the sweaty aroma, and ultimately improved the overall aroma profile. These findings provide insights into the genetic regulation of aroma in fermented soybean products and form a foundation for reducing undesirable aromas and improving the overall aroma quality of industrially produced douchi. Bacillus subtilis fermented soy food is deeply loved by consumers, and its unique aroma characteristics are influenced by the fadA and bkdB genes.
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JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
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2025
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IF 6.2
Xinrui Tang,Abdullah Arsalan,Guoyan Zhang,Junhua Yun,Cunsheng Zhang,Xianghui Qi
D-Allose, a rare sugar, has gained significant attention not only as a low-calorie sweetener but also for its anticancer, antitumor, anti-inflammatory, antioxidant, and other pharmaceutical properties. Despite its potential, achieving high-level biosynthesis of D-allose remains challenging due to inefficient biocatalysts, low conversion rates, and the high cost of substrates. Here, we explored the food-grade coexpression of Blautia produca D-allulose 3-epimerase (Bp-DAE) and Bacillus subtilis L-rhamnose isomerase (BsL-RI) within a single cell using B. subtilis WB800N as the host. Using this system, D-allose was synthesized via a simple, cost-effective, one-pot enzymatic process, employing whole cells as catalysts and D-fructose as the substrate. The system exhibited optimal activity at 65 °C, pH 8.5, with 1 mM Mn2+ and 20 g/L of whole-cell dry weight. Initial production reached 12.5 g/L D-allose with a 12.5% yield from 100 g/L D-fructose. Optimization of dual promoter combinations enhanced production, achieving 15.0, 29.1, and 43.2 g/L D-allose from 100, 200, and 300 g/L D-fructose, with yields of 15.00, 14.55, and 14.40%, respectively. This D-allose production biocatalyst offers a scalable and economically viable platform for the industrial production of rare sugar.
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MICROBIOLOGY
·
2017
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IF 0.856
Faheem Uddin Rajer,Huijun Wu,Yongli Xie,Shanshan Xie,Waseem Raza,Hafiz Abdul Samad Tahir,Xuewen Gao
Rhizobacterial volatile organic compounds (VOCs) play an important role in the suppression of soil-borne phytopathogens. In this study, the VOCs produced by a soil-isolate,Bacillus subtilisFA26, were evaluatedin vitrofor their antibacterial activity againstClavibacter michiganensisssp.sepedonicus(Cms), the causal agent of bacterial ring rot of potato. The VOCs emitted by FA26 inhibited the growth of Cms significantly compared with the control. Scanning and transmission electron microscopy analyses revealed distorted colony morphology and a wide range of abnormalities in Cms cells exposed to the VOCs of FA26. Varying the inoculation strategy and inoculum size showed that the production and activity of the antibacterial VOCs of FA26 were dependent on the culture conditions. Headspace solid-phase microextraction/gas chromatography–mass spectrometry analyses revealed that FA26 produced 11 VOCs. Four VOCs (benzaldehyde, nonanal, benzothiazole and acetophenone) were associated with the antibacterial activity against Cms. The results suggested that the VOCs produced by FA26 could control the causal agent of bacterial ring rot of potato. This information will increase our understanding of the microbial interactions mediated by VOCs in nature and aid the development of safer strategies for controlling plant disease.
研究领域:
植物病理学
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微生物学
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农业科学
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