Novel polyurethane-degrading cutinase BaCut1 from Blastobotrys sp. G-9 with potential role in plastic bio-recycling.

Environmental pollution caused by plastic waste has become global problem that needs to be considered urgently. In the pursuit of a circular plastic economy, biodegradation provides an attractive strategy for managing plastic wastes, whereas effective plastic-degrading microbes and enzymes are required. In this study, we report that Blastobotrys sp. G-9 isolated from discarded plastic in landfills is capable of depolymerizing polyurethanes (PU) and poly (butylene adipate-co-terephthalate) (PBAT). Strain G-9 degrades up to 60% of PU foam after 21 days of incubation at 28 â„ƒ by breaking down carbonyl groups via secretory hydrolase as confirmed by structural characterization of plastics and degradation products identification. Within the supernatant of strain G-9, we identify a novel cutinase BaCut1, belonging to the esterase family, that can reproduce the same effect. BaCut1 demonstrates efficient degradation toward commercial polyester plastics PU foam (0.5 mg enzyme/25 mg plastic) and agricultural film PBAT (0.5 mg enzyme/10 mg plastic) with 50% and 18% weight loss at 37 â„ƒ for 48 h, respectively. BaCut1 hydrolyzes PU into adipic acid as a major end-product with 42.9% recovery via ester bond cleavage, and visible biodegradation is also identified from PBAT, which is a beneficial feature for future recycling economy. Molecular docking, along with products distribution, elucidates a special substrate-binding modes of BaCut1 with plastic substrate analogue. BaCut1-mediated polyester plastic degradation offers an alternative approach for managing PU plastic wastes through possible bio-recycling.

Characterization of a multi-domain exo-ß-1,3-galactanase from Paenibacillus xylanexedens.

ß-1,3-Galactanases selectively degrade ß-1,3-galactan, thus it is an attractive enzyme technique to map high-galactan structure and prepare galactooligosaccharides. In this work, a gene encoding exo-ß-1,3-galactanase (PxGal43) was screened form Paenibacillus xylanexedens, consisting of a GH43 domain, a CBM32 domain and α-L-arabinofuranosidase B (AbfB) domain. Using ß-1,3-galactan (AG-II-P) as substrate, the recombined enzyme expressed in Escherichia coli BL21 (DE3) exhibited an optimal activity at pH 7.0 and 30 °C. The enzyme was thermostable, retaining >70 % activity after incubating at 50 °C for 2 h. In addition, it showed high tolerance to various metal ions, denaturants and detergents. Substrate specificity indicated that PxGal43 hydrolysis only ß-1,3-linked galactosyl oligosaccharides and polysaccharides, releasing galactose as an exo-acting manner. The function of the CBM32 and AbfB domain was revealed by their sequential deletion and suggested that their connection to the catalytic domain was crucial for the oligomerization, catalytic activity, substrate binding and thermal stability of PxGal43. The substrate docking and site-directed mutagenesis proposed that Glu191, Gln244, Asp138 and Glu81 served as the catalytic acid, catalytic base, pKa modulator, and substrate identifier in PxGal43, respectively. These results provide a better understanding and optimization of multi-domain bacterial GH43 ß-1,3-galactanase for the degradation of arabinogalactan.

Genome analysis of a plasmid-bearing myxobacterim Myxococcus sp. strain MxC21 with salt-tolerant property.

Myxobacteria are widely distributed in various habitats of soil and oceanic sediment. However, it is unclear whether soil-dwelling myxobacteria tolerate a saline environment. In this study, a salt-tolerant myxobacterium Myxococcus sp. strain MxC21 was isolated from forest soil with NaCl tolerance >2% concentration. Under 1% salt-contained condition, strain MxC21 could kill and consume bacteria prey and exhibited complex social behaviors such as S-motility, biofilm, and fruiting body formation but adopted an asocial living pattern with the presence of 1.5% NaCl. To investigate the genomic basis of stress tolerance, the complete genome of MxC21 was sequenced and analyzed. Strain MxC21 consists of a circular chromosome with a total length of 9.13 Mbp and a circular plasmid of 64.3 kb. Comparative genomic analysis revealed that the genomes of strain MxC21 and M. xanthus DK1622 share high genome synteny, while no endogenous plasmid was found in DK1622. Further analysis showed that approximately 21% of its coding genes from the genome of strain MxC21 are predominantly associated with signal transduction, transcriptional regulation, and protein folding involved in diverse niche adaptation such as salt tolerance, which enables social behavior such as gliding motility, sporulation, and predation. Meantime, a high number of genes are also found to be involved in defense against oxidative stress and production of antimicrobial compounds. All of these functional genes may be responsible for the potential salt-toleration. Otherwise, strain MxC21 is the second reported myxobacteria containing indigenous plasmid, while only a small proportion of genes was specific to the circular plasmid of strain MxC21, and most of them were annotated as hypothetical proteins, which may have a direct relationship with the habitat adaptation of strain MxC21 under saline environment. This study provides an inspiration of the adaptive evolution of salt-tolerant myxobacterium and facilitates a potential application in the improvement of saline soil in future.

Structural and Functional Properties of Porous Corn Starch Obtained by Treating Raw Starch with AmyM.

Porous starch is attracting considerable attention for its high surface area and shielding ability, properties which are useful in many food applications. In this study, native corn starch with 15, 25, and 45% degrees of hydrolysis (DH-15, DH-25, and DH-45) were prepared using a special raw starch-digesting amylase, AmyM, and their structural and functional properties were evaluated. DH-15, DH-25, and DH-45 exhibited porous surface morphologies, diverse pore size distributions and pore areas, and their adsorptive capacities were significantly enhanced by improved molecular interactions. Structural measures showed that the relative crystallinity decreased as the DH increased, while the depolymerization of starch double helix chains promoted interactions involving disordered chains, followed by chain rearrangement and the formation of sub-microcrystalline structures. In addition, DH-15, DH-25, and DH-45 displayed lower hydrolysis rates, and DH-45 showed a decreased C∞ value of 18.9% with higher resistant starch (RS) content and lower glucose release. Our results indicate that AmyM-mediated hydrolysis is an efficient pathway for the preparation of porous starches with different functionalities which can be used for a range of applications.

Identification and Characterization of Novel Malto-Oligosaccharide-Forming Amylase AmyCf from Cystobacter sp. Strain CF23.

Malto-oligosaccharides (MOSs) from starch conversion is advantageous for food and pharmaceutical applications. In this study, an efficient malto-oligosaccharide-forming α-amylase AmyCf was identified from myxobacter Cystobacter sp. strain CF23. AmyCf is composed of 417 amino acids with N-terminal 41 amino acids as the signal peptide, and conserved glycoside hydrolase family 13 (GH13) catalytic module and predicted C-terminal domain with ß-sheet structure are also identified. Phylogenetic and functional analysis demonstrated that AmyCf is a novel member of GH13_6 subfamily. The special activity of AmyCf toward soluble starch and raw wheat starch is 9249 U/mg and 11 U/mg, respectively. AmyCf has broad substrate specificity toward different types of starches without requiring Ca2+. Under ideal circumstances of 60 °C and pH 7.0, AmyCf hydrolyzes gelatinized starch into maltose and maltotriose and maltotetraose as the main hydrolytic products with more than 80% purity, while maltose and maltotriose are mainly produced from the hydrolysis of raw wheat starch with more than 95% purity. The potential applicability of AmyCf in starch processing is highlighted by its capacity to convert gelatinized starch and raw starch granules into MOSs. This enzymatic conversion technique shows promise for the low-temperature enzymatic conversion of raw starch.

Myxobacteria restrain Phytophthora invasion by scavenging thiamine in soybean rhizosphere via outer membrane vesicle-secreted thiaminase I.

Public metabolites such as vitamins play critical roles in maintaining the ecological functions of microbial community. However, the biochemical and physiological bases for fine-tuning of public metabolites in the microbiome remain poorly understood. Here, we examine the interactions between myxobacteria and Phytophthora sojae, an oomycete pathogen of soybean. We find that host plant and soil microbes complement P. sojae's auxotrophy for thiamine. Whereas, myxobacteria inhibits Phytophthora growth by a thiaminase I CcThi1 secreted into extracellular environment via outer membrane vesicles (OMVs). CcThi1 scavenges the required thiamine and thus arrests the thiamine sharing behavior of P. sojae from the supplier, which interferes with amino acid metabolism and expression of pathogenic effectors, probably leading to impairment of P. sojae growth and pathogenicity. Moreover, myxobacteria and CcThi1 are highly effective in regulating the thiamine levels in soil, which is correlated with the incidence of soybean Phytophthora root rot. Our findings unravel a novel ecological tactic employed by myxobacteria to maintain the interspecific equilibrium in soil microbial community.

Quality Characteristics of Reduced-Fat Emulsified Sausages Made with Yeast Mannoprotein Enzymatically Prepared with a ß-1,6-glucanase.

Mannoproteins, as yeast polysaccharides, have been utilized in food the industry as dietary fibers, emulsifying agents or fat replacers. Mannoprotein MP112, produced from yeast by enzymatic hydrolysis of myxobacterial ß-1,6-glucanase GluM, exhibits excellent emulsifying properties in emulsion preparation. In this study, we aimed to examine the application of stable emulsion with the addition of mannoprotein MP112 (MP112 emulsion) to reduce the fat content of sausages. The addition of MP112 emulsion in emulsified sausages significantly reduced the fat content and increased the moisture and protein contents of emulsified sausages without the expense of their good sensory quality. Moreover, the textural properties of sausages were markedly improved with the higher hardness, chewiness and cohesiveness, especially in the 50-75% replacement ratio of MP112 emulsion. On the other hand, MP112 emulsion replacement of animal fat markedly improved the nutritional composition of emulsified sausages; they displayed a higher PUFA/SFA ratio and lower n-6/n-3 ratio due to their saturated fatty acids being replaced by poly-unsaturated fatty acids. Meanwhile, the oxidative stability of sausages was improved linearly, corresponding to the increased replacement ratio of MP112 emulsion. Our results show that mannoprotein-based emulsions could be used as potential fat alternatives in developing reduced-fat meat products.

Insights into the Antifungal Properties of Myxobacteria Outer Membrane ß-1,6-Glucanase.

Fungal cell wall decomposition enzymes exhibit great potential for the development of efficient antifungal agents. However, their practical application is restricted due to incomplete understanding of the action mode. In our previous study, we identified that a novel outer membrane (OM) ß-1,6-glucanase GluM is deployed by predatory myxobacteria to feed on fungi. In this work, we provide deep insights into the antifungal mechanism of ß-1,6-glucanase and its potential in improving plant disease resistance. The fungal cell wall decomposition ability of GluM resulted in irregular hyphae morphology, changed chitin distribution, increased membrane permeability, and leakage of cell constituents in Magnaporthe oryzae Guy11. Under the attack pattern, the cell wall integrity pathway was activated by strain Guy11 for self-protection. GluM exhibited a distinct endo-model toward fungal cell wall; the favorite substrate of GluM toward fungal ß-1,6-glucan may give reason for its efficient antifungal activity compared with Trichoderma ß-1,6-glucanase. Moreover, released glucans from GluM hydrolysis of fungal cell wall functioned as an elicitor and induced rice immunity by means of jasmonic acid pathway. Based on the dual roles of antifungal properties, gluM transgenic plants conferred enhanced resistance against fungal infection.

Predation of oomycetes by myxobacteria via a specialized CAZyme system arising from adaptive evolution.

As social micropredators, myxobacteria are studied for their abilities to prey on bacteria and fungi. However, their predation of oomycetes has received little attention. Here, we show that Archangium sp. AC19 secretes a carbohydrate-active enzyme (CAZyme) cocktail during predation on oomycetes Phytophthora. These enzymes include three specialized ß-1,3-glucanases (AcGlu13.1, -13.2 and -13.3) that act as a cooperative consortium to target ß-1,3-glucans of Phytophthora. However, the CAZymes showed no hydrolytic effects on fungal cells, even though fungi contain ß-1,3-glucans. Heterologous expression of AcGlu13.1, -13.2 or -13.3 enzymes in Myxococcus xanthus DK1622, a model myxobacterium that antagonizes but does not predate on P. sojae, conferred a cooperative and mycophagous ability that stably maintains myxobacteria populations as a mixture of engineered strains. Comparative genomic analyses suggest that these CAZymes arose from adaptive evolution among Cystobacteriaceae myxobacteria for a specific prey killing behavior, whereby the presence of Phytophthora promotes growth of myxobacterial taxa by nutrient release and consumption. Our findings demonstrate that this lethal combination of CAZymes transforms a non-predatory myxobacterium into a predator with the ability to feed on Phytophthora, and provides new insights for understanding predator-prey interactions. In summary, our work extends the repertoire of myxobacteria predatory strategies and their evolution, and suggests that these CAZymes can be engineered as a functional consortium into strains for biocontrol of Phytophothora diseases and hence crop protection.

[Screening and identification of a polyurethane-degrading bacterium G-11 and its plastic degradation characteristics].

Polyurethane (PUR) plastics is widely used because of its unique physical and chemical properties. However, unreasonable disposal of the vast amount of used PUR plastics has caused serious environmental pollution. The efficient degradation and utilization of used PUR plastics by means of microorganisms has become one of the current research hotspots, and efficient PUR degrading microbes are the key to the biological treatment of PUR plastics. In this study, an Impranil DLN-degrading bacteria G-11 was isolated from used PUR plastic samples collected from landfill, and its PUR-degrading characteristics were studied. Strain G-11 was identified as Amycolatopsis sp. through 16S rRNA gene sequence alignment. PUR degradation experiment showed that the weight loss rate of the commercial PUR plastics upon treatment of strain G-11 was 4.67%. Scanning electron microscope (SEM) showed that the surface structure of G-11-treated PUR plastics was destroyed with an eroded morphology. Contact angle and thermogravimetry analysis (TGA) showed that the hydrophilicity of PUR plastics increased along with decreased thermal stability upon treatment by strain G-11, which were consistent with the weight loss and morphological observation. These results indicated that strain G-11 isolated from landfill has potential application in biodegradation of waste PUR plastics.

[Isolation and identification of a polyester-polyurethane degrading bacterium Bacillus altitudinis YX8-1].

Although polyurethane (PUR) plastics play important roles in daily life, its wastes bring serious environmental pollutions. Biological (enzymatic) degradation is considered as an environmentally friendly and low-cost method for PUR waste recycling, in which the efficient PUR-degrading strains or enzymes are crucial. In this work, a polyester PUR-degrading strain YX8-1 was isolated from the surface of PUR waste collected from a landfill. Based on colony morphology and micromorphology observation, phylogenetic analysis of 16S rDNA and gyrA gene, as well as genome sequence comparison, strain YX8-1 was identified as Bacillus altitudinis. The results of high performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) showed that strain YX8-1 was able to depolymerize self-synthesized polyester PUR oligomer (PBA-PU) to produce a monomeric compound 4, 4'-methylene diphenylamine. Furthermore, strain YX8-1 was able to degrade 32% of the commercialized polyester PUR sponges within 30 days. This study thus provides a strain capable of biodegradation of PUR waste, which may facilitate the mining of related degrading enzymes.

Overexpression of a beta-1,6-glucanase gene GluM in transgenic rice confers high resistance to rice blast, sheath blight and false smut.

BACKGROUND: Frequent fungal diseases tend to lead to severe losses in rice production. As a main component of the fungal cell wall, glucan plays an important role in the growth and development of fungi. Glucanase can inhibit the growth of fungi by breaking glycosidic bonds, and may be a promising target for developing rice varieties with broad-spectrum disease resistance. RESULTS: We transferred a codon-optimized ß-1,6-glucanase gene (GluM) from myxobacteria into the japonica rice variety Zhonghua11 (ZH11), and obtained a large number of individual transgenic plants with GluM overexpression. Based on molecular analysis, three single-copy homozygous lines with GluM overexpression were selected for assessment of fungal disease resistance at the T3 generation. Compared with that of the recipient cultivar ZH11, the area of rice blast lesion in transgenic rice was reduced by 82.71%; that of sheath blight lesion was decreased by 35.76%-43.67%; the sheath blight resistance in the field was enhanced by an average of 0.75 grade over 3 years; and the incidence of diseased panicles due to rice false smut was decreased by 65.79%. More importantly, there was no obvious loss of yield (without a significant effect on agronomic traits). Furthermore, plants overexpressing a ß-1,6-glucanase gene showed higher disease resistance than rice plants overexpressing a ß-1,3-glucanase gene derived from tobacco. CONCLUSION: The ß-1,6-glucanase gene GluM can confer broad-spectrum disease resistance to rice, providing an environmentally friendly alternative way to effectively manage fungal pathogens in rice production. © 2023 Society of Chemical Industry.

Myxobacterial Outer Membrane ß-1,6-Glucanase Induced the Cell Death of Fusarium oxysporum by Destroying the Cell Wall Integrity.

The ß-1,6-glucan is the key linker between mannoproteins in the outermost part of the cell wall and ß-1,3-glucan/chitin polysaccharide to maintain the rigid structure of the cell wall. The ß-1,6-glucanase GluM, which was purified from the fermentation supernatant of Corallococcus sp. EGB, was able to inhibit the germination of Fusarium oxysporum f. sp. cucumerinum conidia at a minimum concentration of 2.0 U/mL (0.08 µg/mL). The survival rates of GluM-treated conidia and monohyphae were 10.4% and 30.7%, respectively, which were significantly lower than that of ß-1,3-glucanase treatment (Zymolyase, 20.0 U/mL; equate to 1.0 mg/mL) (72.9% and 73.9%). In contrast to ß-1,3-glucanase treatment, the high-osmolarity glycerol (HOG) pathway of F. oxysporum f. sp. cucumerinum cells was activated after GluM treatment, and the intracellular glycerol content was increased by 2.6-fold. Moreover, the accumulation of reactive oxygen species (ROS) in F. oxysporum f. sp. cucumerinum cells after GluM treatment induced apoptosis, but it was not associated with the increased intracellular glycerol content. Together, the results indicate that ß-1,6-glucan is a promising target for the development of novel broad-spectrum antifungal agents. IMPORTANCE Phytopathogenic fungi are the most devastating plant pathogens in agriculture, causing enormous economic losses to global crop production. Biocontrol agents have been promoted as replacements to synthetic chemical pesticides for sustainable agriculture development. Cell wall-degrading enzymes (CWDEs), including chitinases and ß-1,3-glucanases, have been considered as important armaments to damage the cell wall. Here, we found that F. oxysporum f. sp. cucumerinum is more sensitive to ß-1,6-glucanase GluM treatment (0.08 µg/mL) than ß-1,3-glucanase Zymolyase (1.0 mg/mL). The HOG pathway was activated in F. oxysporum f. sp. cucumerinum cells after GluM treatment, and the intracellular glycerol content was significantly increased. Moreover, the decomposition of F. oxysporum f. sp. cucumerinum cell wall by GluM induced the burst of intracellular ROS and apoptosis, which eventually leads to cell death. Therefore, we suggest that the ß-1,6-glucan of the fungal cell wall may be a better antifungal target compared to the ß-1,3-glucan.

Characterization of polyhydroxybutyrate (PHB) synthesized by newly isolated rare actinomycetes Aquabacterium sp. A7-Y.

Polyhydroxyalkanoates (PHAs) as biodegradable plastics have attracted increasing attention due to its biodegradable, biocompatible and renewable advantages. Exploitation some unique microbes for PHAs production is one of the most competitive approaches to meet complex industrial demand, and further develop next-generation industrial biotechnology. In this study, a rare actinomycetes strain A7-Y was isolated and identified from soil as the first PHAs producer of Aquabacterium genus. Produced PHAs by strain A7-Y was identified as poly(3-hydroxybutyrate) (PHB) based on its structure characteristics, which is also similar with commercial PHB. After optimization of fermentation conditions, strain A7-Y can produce 10.2 g/L of PHB in 5 L fed-batch fermenter, corresponding with 54 % PHB content of dry cell weight, which is superior to the reported actinomycetes species. Furthermore, the phaCAB operon in stain A7-Y was excavated to be responsible for the efficient PHB production and verified in recombinant Escherichia coli. Our results indicate that strain A7-Y and its biosynthetic gene cluster are potential candidates for developing a microbial formulation for the PHB production.

Preparation of chitooligosaccharides with a low degree of polymerization and anti-microbial properties using the novel chitosanase AqCsn1.

Chitosanases hydrolyze chitosan into chitooligosaccharides (COSs) with various biological activities, which are widely employed in many areas including plant disease management. In this study, the novel chitosanase AqCsn1 belonging to the glycoside hydrolase family 46 (GH46) was cloned from Aquabacterium sp. A7-Y and heterologously expressed in Escherichia coli BL21 (DE3). AqCsn1 displayed the highest hydrolytic activity towards chitosan with 95% degree of deacetylation at 40 °C and pH 5.0, with a specific activity of 13.18 U/mg. Product analysis showed that AqCsn1 hydrolyzed chitosan into (GlcN)2 and (GlcN)3 as the main products, demonstrating an endo-type cleavage pattern. Evaluation of antagonistic activity showed that the hydrolysis products of AqCsn1 suppress the mycelial growth of Magnaporthe oryzae and Phytophthora sojae in a concentration-dependent manner, and the inhibition rate of P. sojae reached 39.82% at a concentration of 8 g/L. Our study demonstrates that AqCsn1 and hydrolysis products with a low degree of polymerization might have potential applications in the biological control of agricultural diseases.

Comparative study on bread quality and starch digestibility of normal and waxy wheat (Triticum aestivum L.) modified by maltohexaose producing α-amylases.

It is highly desirable to produce bread with both acceptable texture and health benefits. In this study, maltohexaose (G6) producing amylase AmyM and its truncation AmyM-TR2 from Corallococcus sp. strain EGB were used to determine their effects to bread quality and starch physicochemical properties. During bread fermentation, AmyM or AmyM-TR2 continuously degraded the starch, resulting in more obvious decrease in relative crystallinity, the ordered structure, pasting viscosities and gelatinization enthalpy of starch than in control. The dough treated with AmyM or AmyM-TR2 increased bread volume and slowly digestible starch content, decreased bread hardness, and extended bread shelf life and as compared with control, and the dough treated with AmyM-TR2 had better improvement effects than AmyM. The volume and slowly digestible starch content of bread from the treatment of AmyM-TR2 increased by 9.74% and 7.56% in normal wheat, 1.42% and 10.28% in waxy wheat as compared with AmyM, respectively. AmyM-TR2 affected the substrate targeting, proximity and structure disruption effects, which contributed to the degradation of more starch than AmyM.

Temporal dynamics of total and active root-associated diazotrophic communities in field-grown rice.

Plant-associated nitrogen-fixing microorganisms (diazotrophs) are essential to host nutrient acquisition, productivity and health, but how host growth affects the succession characteristics of crop diazotrophic communities is still poorly understood. Here, Illumina sequencing of DNA- and RNA-derived nifH genes was employed to investigate the dynamics of total and active diazotrophic communities across rhizosphere soil and rice roots under four fertilization regimes during three growth periods (tillering, heading and mature stages) of rice in 2015 and 2016. Our results indicated that 71.9-77.2% of the operational taxonomic units (OTUs) were both detected at the DNA and RNA levels. According to the nonmetric multidimensional scaling ordinations of Bray-Curtis distances, the variations in community composition of active rhizosphere diazotrophs were greater than those of total rhizosphere diazotrophs. The community composition (ß-diversity) of total and active root-associated diazotrophs was shaped predominantly by microhabitat (niche; R 2 ≥ 0.959, p < 0.001), followed by growth period (R 2 ≥ 0.15, p < 0.001). The growth period had a stronger effect on endophytic diazotrophs than on rhizosphere diazotrophs. From the tillering stage to the heading stage, the α-diversity indices (Chao1, Shannon and phylogenetic diversity) and network topological parameters (edge numbers, average clustering coefficient and average degree values) of total endophytic diazotrophic communities increased. The proportions of OTUs shared by the total rhizosphere and endophytic diazotrophs in rhizosphere diazotrophs gradually increased during rice growth. Moreover, total diazotrophic α-diversity and network complexity decreased from rhizosphere soil to roots. Collectively, compared with total diazotrophic communities, active diazotrophic communities were better indicators of biological response to environmental changes. The host microhabitat profoundly drove the temporal dynamics of total and active root-associated diazotrophic communities, followed by the plant growth period.

Construction and comparison of synthetic microbial consortium system (SMCs) by non-living or living materials immobilization and application in acetochlor degradation.

The microbial degradation of pesticides by pure or mixed microbial cultures has been thoroughly explored, however, they are still difficult to apply in real environmental remediation. Here, we constructed a synthetic microbial consortium system (SMCs) through the immobilization technology by non-living or living materials to improve the acetochlor degradation efficiency. Rhodococcus sp. T3-1, Delftia sp. T3-6 and Sphingobium sp. MEA3-1 were isolated for the SMCs construction. The free-floating consortium with the composition ratio of 1:2:2 (Rhodococcus sp. T3-1, Delftia sp. T3-6 and Sphingobium sp. MEA3-1) demonstrated 94.8% degradation of acetochlor, and the accumulation of intermediate metabolite 2-methyl-6-ethylaniline was decreased by 3 times. The immobilized consortium using composite materials showed synergistic effects on the acetochlor degradation with maximum degradation efficiency of 97.81%. In addition, a novel immobilization method with the biofilm of Myxococcus xanthus DK1622 as living materials was proposed. The maximum 96.62% degradation was obtained in non-trophic media. Furthermore, the immobilized SMCs showed significantly enhanced environmental robustness, reusability and stability. The results indicate the promising application of the immobilization methods using composite and living materials in pollutant-contaminated environments.

A novel cold-active GH8 xylanase from cellulolytic myxobacterium and its application in food industry.

Although xylanase have a wide range of applications, cold-active xylanases have received less attention. In this study, a novel glycoside hydrolase family 8 (GH8) xylanase from Sorangium cellulosum with high activity at low temperatures was identified. The recombinant xylanase (XynSc8) was most active at 50 °C, demonstrating 20% of its maximum activity and strict substrate specificity towards beechwood and corncob xylan at 4 °C with Vmax values of 968.65 and 1521.13 µmol/mg/min, respectively. Mesophilic XynSc8 was active at a broad range of pH and hydrolyzed beechwood and corncob xylan into xylooligosaccharides (XOS) with degree of polymerization greater than 3. Moreover, incorporation of XynSc8 (0.05-0.2 mg/kg flour) provided remarkable improvement (28-30%) in bread specific volume and textural characteristics of bread compared to commercial xylanase. This is the first report on a novel cold-adapted GH8 xylanase from myxobacteria, suggesting that XynSc8 may be a promising candidate suitable for bread making.

Glycogen Branching Enzyme with a Novel Chain Transfer Mode Derived from Corallococcus sp. Strain EGB and Its Potential Applications.

Dietary starch with an increased content of resistant starch (RS) has the potential to reduce the prevalence of diabetes, obesity, and cardiovascular diseases. Here, an efficient glycogen branching enzyme, CcGBE, from Corallococcus sp. strain EGB was identified, and its relevant properties, including potential application in the preparation of modified starch, were evaluated. The purified CcGBE exhibited a maximal specific activity of approximately 20,000 U/mg using cassava starch as the optimal substrate. The content of α-1,6-glucosidic bonds in CcGBE-modified cassava starch increased from 2.9 to 13.2%. Meanwhile, both the average chain length (CL) of CcGBE-modified starch and the blue value of the color complex formed by starch and iodine initially increased and then decreased, indicating that a new CL transfer mode was reported. Perforated small starch granules were released after CcGBE treatment, and a time-dependent decrease in the retrogradation enthalpy (ΔHr) of cassava starch indicated that CcGBE inhibited the long-term retrogradation of starch. Moreover, the RS content and cold water solubility (CWS) of CcGBE-modified starch increased from 3.3 to 12.8% and from 23.1 to 93.8%, respectively. These findings indicate the application potential of CcGBE for the preparation of modified starch with increased RS and CWS.