The Journal of General and Applied Microbiology
Online ISSN : 1349-8037
Print ISSN : 0022-1260
ISSN-L : 0022-1260
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Displaying 1-19 of 19 articles from this issue
  • Yan Liu, Na Shen, Zhige Wu, Yu Yang, Xinyan Dong, Zhihua Jin, Qingchao ...
    Article ID: 2024.03.002
    Published: 2024
    Advance online publication: April 05, 2024
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    In Streptomyces pristinaespiralis, AfsKRS system has differential regulation for PI and PII component biosynthesis of pristinamycin, but it is unknown whether S-adenosylmethionine (SAM) plays an important role in the AfsK-AfsR-AfsS signal transduction cascade during pristinamycin production. The possible target of exogenous SAM in the AfsKRS system and the biological role of SAM during the production of PI and PII were investigated using three mutantsΔafsK,ΔafsR andΔafsS defective in signal cascade pathway of AfsKRS. It was found that external SAM had a significant activation of PI production (1.85-fold increase) but had no obvious effect on PII production in the original strain F618 with the normal response of AfsKRS regulation. Addition of SAM resulted in a similar increase in pristinamycin yield in the mutant with defective afsK or afsR, but induced more crucial activation of PI biosynthesis than PII biosynthesis both in ΔafsK (1.65-fold and 1.15-fold increase respectively) and ΔafsR (1.27-fold and 1.09-fold increase respectively). Exogenous SAM only significantly enhanced PII production in ΔafsS (1.1-fold increase). These results could provide valuable insights into the regulatory function of the AfsKRS system in S. pristinaespiralis.

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  • Ken-ichiro Ohnishi, Seiya Watanabe, Aya Kadoya, Satoru Suzuki
    Article ID: 2024.03.001
    Published: 2024
    Advance online publication: March 27, 2024
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    Supplementary material

    Cellulose is an abundant biomass on the planet. Various cellulases from environmental microbes have been explored for industrial use of cellulose. Marine fish intestine is of interest as one source of new enzymes. Here, we report the discovery of genes encoding two β-glucosidases (Bgl3A and Bgl3B) and four endo-1,4-β-glucanases (Cel5A, Cel8, Cel5B, and Cel9) as part of the genome sequence of a cellulolytic marine bacterium, Microbulbifer sp. Strain GL-2. Five of these six enzymes (excepting Cel5B) are presumed to localize to the periplasm or outer membrane. Transcriptional analysis demonstrated that all six genes were highly expressed in stationary phase. The transcription was induced by cello-oligosaccharides rather than by glucose, suggesting that the cellulases are produced primarily for nutrient acquisition following initial growth, facilitating the secondary growth phase. We cloned the genes encoding two of the endo-1,4-β-glucanases, Cel5A and Cel8, and purified the corresponding recombinant enzymes following expression in Escherichia coli. The activity of Cel5A was observed across a wide range of temperatures (10–40 ˚C) and pHs (6–8). This pattern differed from those of Cel8 and the commercial cellulase Enthiron, both of which exhibit decreased activities below 30 ˚C and at alkaline pHs. These characteristics suggest that Cel5A might find use in industrial applications. Overall, our results reinforce the hypothesis that marine bacteria remain a possible source of novel cellulolytic activities.

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  • Miyo Yamane, Kaori Iwazumi, Takashi Osanai*
    Article ID: 2024.02.003
    Published: 2024
    Advance online publication: February 29, 2024
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    Supplementary material

    Fumarase is an enzyme catalyzing reversible reaction between fumarate and L-malate in the citric acid cycle. Fumarase is used in the industrial production of L-malate, and its immobilization is required for reuse of the fumarases to reduce the cost. Accordingly, understanding the properties of immobilized fumarase is crucial, and several groups report on the storage stability and kinetic parameters of immobilized fumarase. Here we have immobilized fumarase from the thermophilic red alga Cyanidioschyzon merolae (CmFUM) on ceramic beads and investigated its biochemical and physical properties. CmFUM demonstrated sufficient stability and reusability for industry use after immobilization. Notably, the thermostability was dramatically enhanced through immobilization. The Km value and kcat of immobilized CmFUM for fumarate were 1.7 mM and 22.7 s-1 respectively. The Km value for fumarate was lower than that of other reported immobilized fumarases, indicating a high substrate affinity of immobilized CmFUM. Furthermore, the enhanced stability resulting from immobilization partially compensated for the decrease in activity. The high affinity towards fumarate and good thermostability of immobilized CmFUM revealed in this study are advantageous traits for improving enzyme-mediated isomer-specific L-malate production.

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  • Yoko Takahashi
    Article ID: 2024.02.002
    Published: 2024
    Advance online publication: February 28, 2024
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    The culture filtrates of the predominant bacterial strains isolated from soil samples have been shown to increase the microbial colony counts on agar plates used for the isolation of uncultured bacteria. One of the factors in the culture filtrates responsible for this increase was identified to be superoxide dismutase (SOD). The generation of reactive oxygen species (O2-, H2O2, and ・OH) was detected from conventional laboratory agar media. The use of agar media supplemented with radical scavengers (SOD, catalase, ascorbic acid, or rutin) effectively increased the colony counts and kinds of microbial strains that grew from soil samples. Taxonomical studies on these isolates revealed new taxa for phylum Actinomycetota; one family, three genera, and nine species were newly described. One of the strains, Patulibacter minatonensis KV-614T belonging to the new family Patulibacteraceae, was isolated on agar medium supplemented with SOD. P. minatonensis KV-614T represents a novel lineage within the phylum Actinomycetota. A polymerase chain reaction (PCR) study using specific primers for the detection of strains related to the genus Patulibacter, order Solirubrobacterales, showed a high distribution frequency, with detection in over 70% of the soil samples tested. These data suggest that the use of radical scavengers may facilitate the isolation of some hitherto-uncultivated microorganisms widely distributed in soil.

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  • Yui Horaguchi, Moe Yokomichi, Masaki Takahashi, Fusheng Xu, Hiroyuki K ...
    Article ID: 2024.02.001
    Published: 2024
    Advance online publication: February 13, 2024
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    Supplementary material

    The glycoside hydrolase (GH) 71 α-1,3-glucanase (Agn1p) from Schizosaccharomyces pombe consists of an N-terminal signal sequence and a catalytic domain. Meanwhile, the GH87 α-1,3-glucanase (Agl-KA) from Bacillus circulans KA-304 consists of an N-terminal signal sequence, a first discoidin domain (DS1), a carbohydrate-binding module family 6 (CBM6), a threonine and proline repeat linker (TP), a second discoidin domain (DS2), an uncharacterized domain, and a catalytic domain. DS1, CBM6, and DS2 exhibit α-1,3-glucan binding activity. This study involved genetically fusing TP, DS1, CBM6, TP, and DS2 to the C-terminus of Agn1p, generating the fusion enzyme Agn1p-DCD. The fusion enzyme was then expressed in Escherichia coli and purified from the cell-free extract. Agn1p-DCD and Agn1p exhibited similar characteristics, such as optimal pH, optimal temperature, pH stability, and thermostability. Insoluble α-1,3-glucan (1%) hydrolyzing assay showed that Agn1p-DCD and Agn1p released approximately 7.6 and 5.0 mM of reducing sugars, respectively, after 48 h of reaction. Kinetic analysis and an α-1,3-glucan binding assay indicated that the addition of DS1, CBM6, and DS2 enhanced the affinity of Agn1p for α-1,3-glucan. Moreover, Agn1p-DCD contributed to enhancing the fungal growth inhibition activity when combined with a mixture of GH19 chitinase and GH16 β-1,3-glucanase.

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  • Taro Watanabe, Yuki Kimura, Daisuke Umeno
    Article type: research-article
    Article ID: 2024.01.002
    Published: 2024
    Advance online publication: January 29, 2024
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    Supplementary material

    S-adenosylmethionine (SAM) is an important biomolecule that mainly acts as a methyl donor and plays many roles in a variety of biological functions. SAM is also required for the biosynthesis of valuable methylated compounds, but its supply is a bottleneck for these biosynthetic pathways. To overcome this bottleneck and to reconfigure SAM homeostasis, a high-throughput sensing system for changes in intracellular SAM availability is required. We constructed a plasmid that can detect the factors that can alter SAM availability using minimal components. It does so by placing a fluorescent protein under a promoter controlled by endogenous MetJ, a transcription factor that represses its own regulons upon binding with SAM. Next, to validate SAM-responsive behavior, we systematically reconstructed 10 synthetic promoters with different positions and with different number of metbox sites, sequences of MetJ binding. We found that a position between the −35 box and the −10 box was the most effective for repression and that this setup was suitable for detecting the genetic or environmental factors that can deplete and recover the intracellular SAM availability. Overall, the response patterns of the synthetic MetJ-regulated promoters characterized in this study may be useful for the development of further SAM biosensing systems.

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  • Kazuya Kobayashi, Natsuka Takada, Yuki Matsubara, Hiroaki Okuhara, M ...
    Article type: research-article
    Article ID: 2024.01.003
    Published: 2024
    Advance online publication: January 29, 2024
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    Supplementary material

    To enhance the value of surimi, efforts have been made to develop a fermentation method with lactic acid bacteria (LAB) to proteolyze fish protein. However, fermenting unheated surimi poses a spoilage risk due to its high bacterial content. Surimi heat treatment can prevent spoilage, but gel formation induced by heating introduces another technical issue: it hinders uniform fermentation. Thus, this study aims to observe the proteolysis and enhance the functionality of seafood product through lactic acid fermentation of kamaboko, a heated surimi. Upon analyzing the kamaboko fermented with Lactobacillus helveticus JCM1004, we observed that LAB produced protease, resulting in the degradation of myosin heavy chain and actin during fermentation. Lactic acid fermentation significantly augmented the peptide content of kamaboko, subsequently elevating the angiotensin Ⅰ-converting enzyme (ACE) inhibitory activity in 200-fold diluted extract of fermented kamaboko to approximately 70% and higher. Notably, our investigation revealed that proteolysis was confined to the surface of kamaboko, as evidenced by SDS-PAGE analysis. This observation implies that the surface area of kamaboko influences the ACE inhibitory activity. Through a comparative analysis of various bacterial strains, we demonstrated that the increase in ACE inhibitory activity is contingent on the protease generated by LAB. These results suggest that LAB-mediated proteolysis of fish proteins liberates bioactive peptides, thereby manifesting in the ACE inhibitory activity. In summary, this study underscores that the fermentation of kamaboko employing proteolytic LAB holds promise in the development of novel functional seafood products.

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  • Atsuko Hishida, Ryo Shirai, Akiyoshi Higo, Minenosuke Matsutani, Kaor ...
    Article type: research-article
    Article ID: 2024.01.001
    Published: 2024
    Advance online publication: January 23, 2024
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    Supplementary material

    Most cyanobacterial genomes possess more than two copies of genes encoding cyAbrBs (cyanobacterial AbrB-like proteins) having an AbrB-like DNA-binding domain at their C-terminal region. Accumulating data suggest that a wide variety of metabolic and physiologic processes are regulated by cyAbrBs. In this study, we investigated the function of the essential gene cyabrB1 (sll0359) in Synechocystis sp. PCC 6803 by using CRISPR interference technology. The conditional knockdown of cyabrB1 caused increases of cyAbrB2 transcript and protein levels. However, the effect of cyabrB1 knockdown on global gene expression profile was quite limited compared to the previously reported profound effect of knockout of cyabrB2. Among 24 up-regulated genes, 16 genes were members of the divergently transcribed icfG and sll1783 operons related to carbon metabolism. The results of this and previous studies indicate the different contributions of two cyAbrBs to transcriptional regulation of genes related to carbon, hydrogen and nitrogen metabolism. Possession of a pair of cyAbrBs has been highly conserved during the course of evolution of the cyanobacterial phylum, suggesting physiological significance of transcriptional regulation attained by their interaction.

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  • Kristen Conroy, Jelmer Poelstra, Karen Mancl
    Article type: research-article
    Article ID: 2023.12.003
    Published: 2024
    Advance online publication: January 18, 2024
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    High salt wastewater is produced in industries, including seafood and pickling processing. The salinity in such wastewaters has been shown to negatively impact biological treatment efficacy. Little is known about the changes in the microbial community structure in the mature biological treatment systems, the impacts of salinity on community composition, and the shifts over time during operation. Specifically, intermittent sand bioreactors (ISBs) with a focus on ammonia treatment were utilized. This study aimed to identify the changes in the microbial community due to both salt and days of operation through 16s rRNA sequencing and KEGG functional predictions. Results showed that the overall community structure and diversity were distinct as wastewater salinity varied from 0%-1.3%. At 1.3% salinity Zoogloea, a common genus in wastewater treatment plants, was not present and Aequorovita, Thaura and Dokdonella became the dominant genera. Nitrosomonas, an important ammonia oxidizing bacteria, increased in abundance with days of operation but was not significantly impacted by an increase in salinity. This finding was further supported by an increase in predicted nitrification potential with time of operation within all intermittent sand bioreactors tested. These results provide a deeper understanding of the impacts of salinity on microbial community development in biological treatment systems and elucidate the shifts in community structure occurring during early operations and into system maturity.

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  • Olga Gladyshchuk, Masaki Yoshida, Koume Togashi, Hayuki Sugimoto, Kaz ...
    Article type: research-article
    Article ID: 2023.12.004
    Published: 2024
    Advance online publication: January 18, 2024
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    Supplementary material

    We investigated the presence and functionality of the carbon storage regulator (Csr) system in Aeromonas salmonicida SWSY-1.411. CsrA, an RNA-binding protein, shared 89% amino acid sequence identity with Escherichia coli CsrA. CsrB/C sRNAs exhibited a typical stem-loop structure, with more GGA motifs, which bind CsrA, than E. coli. CsrD had limited sequence identity with E. coli CsrD; however, it contained the conserved GGDEF and EAL domains. Functional analysis in E. coli demonstrated that the Csr system of A. salmonicida influences glycogen biosynthesis, biofilm formation, motility, and stability of both CsrB and CsrC sRNAs. These findings suggest that in A. salmonicida, the Csr system affects phenotypes like its E. coli counterpart. In A. salmonicida, defects in csr homologs affected biofilm formation, motility, and chitinase production. However, glycogen accumulation and protease production were unaffected. The expression of flagellar-related genes and chitinase genes was suppressed in the csrA-deficient A. salmonicida. Northern blot analysis indicated the stabilization of CsrB and CsrC in the csrD-deficient A. salmonicida. Similar to that in E. coli, the Csr system in A. salmonicida comprises the RNA-binding protein CsrA, the sRNAs CsrB and CsrC, and the sRNA decay factor CsrD. This study underscores the conservation and functionality of the Csr system and raises questions about its regulatory targets and mechanisms in A. salmonicida.

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  • Kailu Zhang, Hui Zhou, Juntao Ke, Hongli Feng, Cunlong Lu, Shaoxing Ch ...
    Article ID: 2023.12.002
    Published: 2024
    Advance online publication: January 15, 2024
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    Supplementary material

    Phthalates esters (PAEs) are a kind of polymeric material additives widely been added into plastics to improve products’ flexibility. It can easily cause environmental pollution which are hazards to public health. In this study, we isolated an efficient PAEs degrading strain, Janthinobacterium sp. E1, and determined its degradation effect of di-2-ethylhexyl phthalate (DEHP) under stress conditions. Strain E1 showed an obvious advantage in pollutants degradation under various environmental stress conditions. Degradation halo clearly occurred around the colony of strain E1 on agar plate supplemented with triglyceride. Strain E1’s esterase is a constitutively expressed intracellular enzyme. The esterase purified from strain E1 showed a higher catalytic effect on short-chain PAEs than long-chain PAEs. The input of DEHP, DBP (dibutyl phthalate) and DMP (dimethyl phthalate) into the tested soil did not change the species composition of soil prokaryotic community, but altered the dominant species in specific environmental conditions. And the community diversity and richness decreased to a certain extent. However, the diversity and richness of the microbial community were improved after the contaminated soil was treated with the strain E1. Our results also suggested that strain E1 exhibited a tremendous potential in environmental bioremediation in the real environment, which provides a new insight into the elimination of the pollutants contamination in the urban environment.

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  • Ana Edith Ayala-Rodríguez, Silvia Valdés-Rodríguez, Víctor Enrique Ola ...
    Article ID: 2023.12.001
    Published: 2023
    Advance online publication: December 15, 2023
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    Supplementary material

    Bacteria represent an attractive source for the isolation and identification of potentially useful microorganisms for lignin depolymerization, a process required for the use of agricultural waste. In this work, ten autochthonous bacteria isolated from straw, cow manure, and composts were characterized for potential use in the biodelignification of the waste. A comparison of the ability to degrade lignin and the efficiency of ligninolytic enzymes was performed in bacteria grown in media with lignin as a sole carbon source (LLM, 3.5g/L lignin-alkali) and in complex media supplemented with All-Ban fiber (FLM, 1.5g/L). Bacterial isolates showed different abilities to degrade lignin, they decreased the lignin concentration from 7.6 to 18.6% in LLM and from 11.1 to 44.8% in FLM. They also presented the activity of manganese peroxidase, lignin peroxidases, and laccases with different specific activities. However, strain 26 identified as Paenibacillus polymyxa by sequencing the 16S rRNA showed the highest activity of lignin peroxidase and the ability to degrade efficiently lignocellulose. In addition, P. polymyxa showed the highest potential (desirability ≥ 0.795) related to the best combination of properties to depolymerize lignin from biomass. The results suggest that P. polymyxa has a coordinated lignin degradation system constituted of lignin peroxidase, manganese peroxidase, and laccase enzymes.

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  • Jinming Liu, Shiyu Zhang, Haikun Ma, Jun Huang, Meichun Xiang, Xin ...
    Article type: research-article
    Article ID: 2023.11.001
    Published: 2023
    Advance online publication: November 21, 2023
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    Phytophthora species are highly destructive soilborne oomycetes pathogens that spread through infested soil and water. Ochrobactrum pseudogrignonense NC1 has been shown to inhibit plant parasitic nematodes via volatile organic compounds (VOCs). In this study, we investigated the inhibitory effect of O. pseudogrignonense NC1 against four Phytophthora species on agar plates and in vivo bioassay. We found that NC1 significantly inhibited the mycelial growth and zoospore production of all four species of Phytophthora in a dose-dependent manner. The half maximal inhibitory concentration (IC50) values for inhibition of mycelial growth (or zoospore production) were 26% (14.8%), 18.9% (14.2%), 20.3% (8.3%) and 46.9% (4%) for Phytophthora capsici Leonian, Phytophthora infestans, Phytophthora parasitica var. nicotiana and Phytophthora sojae, respectively. The biocontrol efficiency of NC1 was 46.3% in pepper seedlings against P. capsici, almost 100% in potato tubers against P. infestans, 60% in tomato leave against P. parasitica and 100% in soybean leave against P. sojae, respectively. Our findings suggest that O. pseudogrignonense NC1 has great potential as a biocontrol agent for managing Phytophthora diseases.

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  • Akinori Kato
    Article type: research-article
    Article ID: 2023.10.001
    Published: 2023
    Advance online publication: November 07, 2023
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    There are a number of reporter systems that are useful for gene expression analysis in bacteria. However, at least in Salmonella, a versatile and simple luciferase reporter system that can be integrated precisely behind a promoter or gene of interest on a chromosome is not currently available. The luciferase operon luxCDABE from Photorhabdus luminescens has several advantages, including brightness, wide linear range, absence in most bacteria, stability at high temperature, and no substrate addition required for the assay. Here, a conjugation-mediated site-specific single-copy luciferase fusion system is developed. A reporter plasmid containing the conditional replication origin R6Kgγ, FRT-luxCDABE, and KmR marker was designed to be incorporated into the FRT site behind the promoter or gene of interest on the chromosome in cells expressing FLP. However, when this reporter plasmid was electroporated directly into such a S. enterica strain, no colonies appeared, likely due to the low transformation efficiency of this relatively large plasmid DNA. Meanwhile, the same reporter plasmid was successfully introduced and launched as an insert of an FRT-containing conjugative transfer plasmid from a mating E. coli strain to the same recipient S. enterica strain, as well as Citrobacter koseri. RcsB-dependent inducible luminescence from the constructed wzc-luxCDABE strains was confirmed. This system is feasible for detecting very low levels of transcription, even in Gram-negative bacterial species that are relatively difficult to genetically manipulate.

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  • Man Hao, Chaoshuo Shi, Weifeng Gong, Jia Liu, Xiangxin Meng, Fufeng ...
    Article type: research-article
    Article ID: 2023.09.002
    Published: 2023
    Advance online publication: October 26, 2023
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    Supplementary material

    Proteolytic enzymes stand out as the most widely employed category utilized in manufacturing industry. A new protease was separated from Planococcus sp.11815 strain and named as nprS-15615 in this research. The gene of this protease has not been reported, and its enzymatic properties have been studied for the first time. To enhance enzyme production, the Planococcus sp. protease gene was expressed in Bacillus licheniformis 2709. The expression level of nprS-15615 was observed under the control of regulatory elements PaprE. nprS-15615 protease activity reached 1186.24±32.87 U/mL after 48 hours of cultivation in shake flasks which was nearly four times the output of the original bacteria (291.38±25.73U/mL). The optimum temperature and pH of the recombinant protease were 30 ℃ and 8.0, respectively.The enzyme exhibited the highest capacity for hydrolyzing casein and demonstrated resilience towards a NaCl concentration of 10.0% (wt/v). Furthermore, in the presence of 0.5% surfactants, the recombinant protease activity can maintain above 75%, and with the existence of 0.5% liquid detergents, there was basically no loss of enzyme activity which indicated that nprS-15615 had good compatibility with surfactants and liquid detergents. In addition, npS-15615 performed well in the washing experiment, and the washing effect at 20 ℃ can be significantly improved by adding crude enzyme solution in the washing process.

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  • Hokuto Ohtsuka, Sawa Kawai, Yoko Otsubo, Takafumi Shimasaki, Akira ...
    Article type: research-article
    Article ID: 2023.09.001
    Published: 2023
    Advance online publication: October 06, 2023
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    Supplementary material

    The fission yeast Schizosaccharomyces pombe ecl family genes respond to various starvation signals and induce appropriate intracellular responses, including the extension of chronological lifespan and induction of sexual differentiation. Herein, we propose that the colonization of hemocoel 1 (COH1) protein of Metarhizium robertsii, an insect-pathogenic fungus, is a functional homolog of S. pombe Ecl1 family proteins.

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  • Nozomi Katsuki, Shunsuke Masuo, Noriyuki Nukui, Hajime Minakawa, Naoki ...
    Article type: research-article
    Article ID: 2023.08.004
    Published: 2023
    Advance online publication: August 30, 2023
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    Plant-derived phenolic gallic acid (GA) is an important raw material for antioxidants and food additives. Efforts to ferment GA using microbial processes have aimed at minimizing production costs and environmental load using enzymes that hydroxylate p-hydroxybenzoate and protocatechuate (PCA). Here, we found a p-hydroxybenzoate hydroxylase (PobA) in the bacterium Hylemonella gracilis NS1 (HgPobA) with 1.5-fold more hydroxylation activity than that from Pseudomonas aeruginosa PAO1 and thus converted PCA to GA more efficiently. The PCA hydroxylation activity of HgPobA was improved by introducing the amino acid substitutions L207V/Y393F or T302A/Y393F. These mutants had 2.9- and 3.7-fold lower Kmapp for PCA than wild-type HgPobA. An Escherichia coli strain that reinforces shikimate pathway metabolism and produces HgPobA when cultured for 60 h generated 0.27 g L-1 of GA. This is the first report of fermenting glucose to generate GA using a natural enzyme from the PobA family. The E. coli strain harboring the HgPobA L207V/Y393F mutant increased GA production to 0.56 g L-1. During the early stages of culture, GA was fermented at a 10-fold higher rate by a strain producing either HgPobA L207V/Y393F or T302A/Y393F compared with wild-type HgPobA, which agreed with the high kcatapp/Kmapp PCA values of this mutant. We enhanced a PobA isozyme and its PCA hydroxylating function to efficiently and cost-effectively ferment GA.

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  • Dina Barman, Mamtaj S. Dkhar
    Article type: research-article
    Article ID: 2023.08.001
    Published: 2023
    Advance online publication: August 25, 2023
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    Supplementary material

    Endophytic actinobacteria are known to produce various enzymes with potential industrial applications. Alpha-amylase is an important class of industrial enzyme with a multi-dimensional utility. The present experiment was designed to characterize a moderately thermostable α-amylase producing endophytic Streptomyces mobaraensis DB13 isolated from Costus speciosus (J. Koenig) Sm. The enzyme was purified using 60% ammonium sulphate precipitation, dialysis, and Sephadex G-100 column chromatography. Based on 12% SDS-PAGE, the molecular weight of the purified α-amylase was estimated to be 55 kDa. The maximum α-amylase activity was achieved at pH 7.0, 50°C and it retained 80% of its activity at both pH 7.0 and 8.0 after incubation for 2 h. The α-mylase activity is strongly enhanced by Ca2+, Mg2+, and inhibited by Ba2+. The activity remains stable in the presence of Tween-80, SDS, PMSF, and Triton X-100; however, β-mercaptoethanol, EDTA, and H2O2 reduced the activity. The kinetic parameters Km and Vmax values for this α-amylase were calculated as 2.53 mM and 29.42 U/mL respectively. The α-amylase had the ability to digest various raw starches at a concentration of 10 mg/mL at pH 7.0, 50°C, where maize and rice are the preferred substrates. The digestion starts after 4 h of incubation, which reaches maximum after 48 h of incubation. These results suggest that S. mobaraensis DB13 is a potential source of moderately thermostable α-amylase enzyme, that effciently hydrolyzes raw starch. It suggesting that this α-amylase is a promising candidate to be use for industrial purposes.

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  • A high-temperature sensitivity of Synechococcus elongatus PCC 7942 due to a tRNA-Leu mutation
    Article ID: 2023.03.001
    Published: 2023
    Advance online publication: March 10, 2023
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