Agricultural waste is as an alternative low-cost carbon source or beneficial additives which catch most people’s eyes. In addition, methanol and sweet potato vine hydrolysate (SVH) have been reported as the efficient enhancers of fermentation according to some reports. The objective of the present study was to confirm SVH as an efficient additive in CA production and explore the synergistic effects of methanol and SVH in fermentation reactions.The optimal fermentation conditions resulted in a maximum citric acid concentration of 3.729 g/L. The final citric acid concentration under the optimized conditions was increased by 3.6-fold over the original conditions, 0.49-fold over the optimized conditions without methanol, and 1.8-fold over the optimized conditions in the absence of SVH. Kinetic analysis showed that Qp, Yp/s, and Yx/s in the optimized systems were significantly improved compared with those obtained in the absence of methanol or SVH. Further, scanning electron microscopy (SEM) revealed that methanol stress promoted the formation of conidiophores, while SVH could neutralize the effect and prolong Aspergillus niger vegetative growth. Cell viability analysis also showed that SVH might eliminate the harmful effects of methanol and enhance cell membrane integrity.SVH was a superior additive for organic acid fermentation, and the combination of methanol and SVH displayed a significant synergistic effect. The research provides a preliminary theoretical basis for SVH practical application in the fermentation industry.

Agricultural waste is as an alternative low-cost carbon source or beneficial additives which catch most people’s eyes. In addition, methanol and sweet potato vine hydrolysate (SVH) have been reported as the efficient enhancers of fermentation according to some reports. The objective of the present study was to confirm SVH as an efficient additive in CA production and explore the synergistic effects of methanol and SVH in fermentation reactions.The optimal fermentation conditions resulted in a maximum citric acid concentration of 3.729 g/L. The final citric acid concentration under the optimized conditions was increased by 3.6-fold over the original conditions, 0.49-fold over the optimized conditions without methanol, and 1.8-fold over the optimized conditions in the absence of SVH. Kinetic analysis showed that Qp, Yp/s, and Yx/s in the optimized systems were significantly improved compared with those obtained in the absence of methanol or SVH. Further, scanning electron microscopy (SEM) revealed that methanol stress promoted the formation of conidiophores, while SVH could neutralize the effect and prolong Aspergillus niger vegetative growth. Cell viability analysis also showed that SVH might eliminate the harmful effects of methanol and enhance cell membrane integrity.SVH was a superior additive for organic acid fermentation, and the combination of methanol and SVH displayed a significant synergistic effect. The research provides a preliminary theoretical basis for SVH practical application in the fermentation industry.

Cupriavidus basilensis is a species with diverse metabolic capabilities, including degradation of xenobiotics and heavy metal resistance. Although the genomes of several strains of this species have been sequenced, no plasmid has yet been constructed for genetic engineering in this species. In this study, we identified a novel plasmid, designated pWS, from C. basilensis WS with a copy number of 1–3 per cell and a length of 2150 bp. pWS contained three protein-coding genes, among which only rep was required for plasmid replication. Rep showed no homology with known plasmid replication initiators. Unlike most plasmids, pWS did not have a cis-acting replication origin outside the region of rep. The minimal replicon of pWS was stable in C. basilensis WS without selection. A conjugative C. basilensis/Escherichia coli shuttle vector, pCB5, was constructed using the minimal replicon of pWS. Interestingly, the copy number of pCB5 was flexible and could be manipulated. Enhancing the expression level of Rep in pCB5 by either doubling the promoter or coding region of rep resulted in doubling of the plasmid copy number. Moreover, replacing the native promoter of rep with the lac promoter increased the copy number by over fivefold. Finally, using two different β-galactosidase reporting systems constructed with pCB5, we successfully demonstrated the different regulatory patterns of bph and dmp operons during diphenyl ether (DE) degradation in C. basilensis WS. Thus, this shuttle vector provided an efficient tool for DNA cloning and metabolic engineering in C. basilensis.

•Carbon sources influence the algicidal activity of Citrobacter sp. R1 against M. aeruginosa.•The algicidal molecular mechanism was successfully illuminated.•Gene glgA was firstly proven to be an algicidal key gene.•The transcriptional level of glg A did not directly control the algicidal activity of strain R1.•Gene glgA exerts algicidal activity at protein translational level.Algicidal bacteria offer a promising option for killing Microcystis aeruginosa, one notorious cyanobacteria causing harmful algal blooms. In this study, Citrobacter sp. R1 presented high algicidal activity (81.6 ± 2.2%, 72 h) against M. aeruginosa when cultured using glucose, while it showed no algicidal activity (0 ± 3.4%) when cultured using wheat bran, suggesting that appropriate carbon source is crucial for algicidal bacteria in killing M. aeruginosa. The underlying algicidal mechanism of strain R1 was explored by studying the effect of different carbon sources (glucose and wheat bran) on its key algicidal gene expression and total protein translation. While the glycogen synthase gene (glgA), cloned from strain R1 via transposon mutagenesis, was for the first time related to algicidal activity, its transcriptional level was not positively correlated with the algicidal activity of strain R1. We found that, the translation of total protein of strain R1 was relatively less when cultured with glucose, compared to growth with wheat bran. This indicated that the functional algicidal gene of strain R1 exerts its algicidal activity at protein translational level. These findings not only reveal the importance of appropriate carbon source for strain R1 for controlling M. aeruginosa, but also bring insights into its underlying algicidal mechanism.Download high-res image (152KB)Download full-size image

•Magnetic kaolin is efficient for treating crystal violet in water.•Adsorption occurred via an exothermal, spontaneous physical process.•Fe3O4 not only endow kaolin magnetism but also enhance its adsorption capacity.•The enhancement mechanism for adsorption capacity was clarified.Kaolin has potential in wastewaters treatment due to its advantage of nontoxicity to aquatic flora and fauna. However, its adsorption capacity needs significant improvement, in addition, the re-collection of adsorbents after application can reduce the risk of desorption of pollutants. Therefore, nanoparticle-modified kaolin (NMK) was prepared by coating kaolin with Fe3O4 nanoparticles to enhance the adsorption capacity of kaolin for crystal violet (CV) in this study. Fe3O4 nanoparticles improved the adsorption capacity of kaolin by at least an order of magnitude, with a maximum capacity of 247.68 ± 4.56 mg CV/g NMK with the initial CV concentration of 800 mg/L; additionally, nanoparticles endowed NMK a magnetization of 21.20 emu/g, indicating that NMK has a magnetic re-collection potential. Spectroscopic analysis demonstrates that the epoxy groups in kaolin are likely the link to the nanoparticles, and the aromatic CC and CO groups of NMK could be responsible for CV adsorption. The enhanced adsorption capacity mechanism of NMK is attributed to nanoparticles decreased zeta potential and changed porous surface characteristics of virgin kaolin. The results suggest that some materials can become more effective in environmental applications via modification by nanoparticles.Download high-res image (222KB)Download full-size image

•Rhodococcus sp. D-1 was isolated as an efficient MBC-degrading bacterium.•Genome of D-1 was analyzed and the general MBC biodegradation pathway was proposed.•Rhamnolipid promoted MBC biodegradation and detoxification in a concentration-dependent manner.•Emulsification and favorable changes in cell surface characteristics facilitated MBC degradation of D-1.We successfully isolated Rhodococcus sp. D-1, an efficient carbendazim-degrading bacterium that degraded 98.20% carbendazim (200 ppm) within 5 days. Carbendazim was first processed into 2-aminobenzimidazole, converted to 2-hydroxybenzimidazole, and then further mineralized by subsequent processing. After genomic analysis, we hypothesized that D-1 may express a new kind of enzyme capable of hydrolyzing carbendazim. In addition, the effect of the biodegradable biosurfactant rhamnolipid on the rate and extent of carbendazim degradation was assessed in batch analyses. Notably, rhamnolipid affected carbendazim biodegradation in a concentration-dependent manner with maximum biodegradation efficiency at 50 ppm (at the critical micelle concentration, CMC) (97.33% degradation within 2 days), whereas 150 ppm (3 CMC) rhamnolipid inhibited initial degradation (0.01%, 99.26% degradation within 2 and 5 days, respectively). Both carbendazim emulsification and favorable changes in cell surface characteristics likely facilitated its direct uptake and subsequent biodegradation. Moreover, rhamnolipid facilitated carbendazim detoxification. Collectively, these results offer preliminary guidelines for the biological removal of carbendazim from the environment.Download high-res image (161KB)Download full-size image

•Consortium NP-M2 could degrade and detoxify nonylphenol effectively.•The addition of organic matter promoted biodegradation.•Secreted surface-active compounds might facilitate biodegradation.•The degradation pathway for NP by NP-M2 was proposed.•Bacterial composition was analyzed using the 16S rDNA library.Nonylphenol (NP), ubiquitously detected as the degradation product of nonionic surfactants nonylphenol polyethoxylates, has been reported as an endocrine disrupter. However, most pure microorganisms can degrade only limited species of NP with low degradation efficiencies. To establish a microbial consortium that can effectively degrade different forms of NP, in this study, we isolated a facultative microbial consortium NP-M2 and characterized the biodegradation of NP by it. NP-M2 could degrade 75.61% and 89.75% of 1000 mg/L NP within 48 h and 8 days, respectively; an efficiency higher than that of any other consortium or pure microorganism reported so far. The addition of yeast extract promoted the biodegradation more significantly than that of glucose. Moreover, surface-active compounds secreted into the extracellular environment were hypothesized to promote high-efficiency metabolism of NP. The detoxification of NP by this consortium was determined. The degradation pathway was hypothesized to be initiated by oxidization of the benzene ring, followed by step-wise side-chain biodegradation. The bacterial composition of NP-M2 was determined using 16S rDNA library, and the consortium was found to mainly comprise members of the Sphingomonas, Pseudomonas, Alicycliphilus, and Acidovorax genera, with the former two accounting for 86.86% of the consortium. The high degradation efficiency of NP-M2 indicated that it could be a promising candidate for NP bioremediation in situ.Download high-res image (179KB)Download full-size image

Biodegradation of triphenylmethane dyes by microorganisms is hampered by the transport barrier imposed by cell membranes. On the other hand, cell-free systems using enzyme-based biodegradation strategy are costly. Therefore, an efficient and inexpensive approach circumventing these problems is highly desirable. Here, we constructed a self-sufficient system for synthetic dye removal by coupling of spore surface-displayed triphenylmethane reductase (TMR) and glucose 1-dehydrogenase (GDH) for the first time. Display of both TMR and GDH significantly enhanced their stability under conditions of extreme pH and temperature. These engineered spores also exhibited more robust long-term stability than their purified counterparts. Furthermore, we observed that a high ratio of spore-displayed GDH is necessary for high dye degradation efficiency. These results indicate that this continuous dye removal system with cofactor regeneration offers a promising solution for dye biodegradation applications.

•B. amyloliquefaciens biofilm was used for the first time to treat CV pollution.•The maximum adsorption capacity of 582.41 mg/g is the largest reported to date.•The adsorption resulted from both intraparticle diffusion and surface adsorption.•Adsorption occurred via an exothermal, spontaneous physical adsorption process.•Micropore diffusion was the rate-limiting step.Bacillus amyloliquefaciens biofilm shows promise for use in the control of soil-borne pathogens; however, it has never been used to treat dye-polluted wastewaters. Here, we propose the novel idea of using B. amyloliquefaciens biofilm for the adsorption of crystal violet (CV) from liquids. The relative contents of three main elements (C1s, O1s, and N1s) in the biofilm were 65.55%, 21.21%, and 13.24%, respectively. The results of Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy revealed that the biofilm contained β-type heteropolysaccharide and proteins. The ruggedness of the biofilm surface due to embedded bacterial cells suggested potential adsorption sites for CV molecules. The maximum capacity for CV adsorption was 582.41 mg/g, which is the largest value reported to date for any CV adsorbent. Blueshift occurred in the FTIR spectrum of CV-loaded biofilm as compared to that of virgin biofilm, confirming a physical adsorption process. We found that CV adsorption by biofilm was complex and resulted from intraparticle diffusion as well as surface adsorption. Our data also suggested that the process is exothermal and spontaneous, with micropore diffusion as the rate-limiting step. These findings provide a basis for using B. amyloliquefaciens biofilm as an efficient adsorbent for treating CV-polluted wastewaters.

A phosphite dehydrogenase gene (ptdhK) consisting of 1,011-bp nucleotides which encoding a peptide of 336 amino acid residues was cloned from Pseudomonas sp. K. gene ptdhK was expressed in Escherichia coli BL21 (DE3) and the corresponding recombinant enzyme was purified by metal affinity chromatography. The recombinant protein is a homodimer with a monomeric molecular mass of 37.2 kDa. The specific activity of PTDH-K was 3.49 U mg−1 at 25 °C. The recombinant PTDH-K exhibited maximum activity at pH 3.0 and at 40 °C and displayed high stability within a wide range of pHs (5.0 to 10.5). PTDH-K had a high affinity to its natural substrates, with Km values for sodium phosphite and NAD of 0.475 ± 0.073 and 0.022 ± 0.007 mM, respectively. The activity of PTDH-K was enhanced by Na+, NH4+, Mg2+, Fe2+, Fe3+, Co2+, and EDTA, and PTDH-K exhibited different tolerance to various organic solvents.

The main objective of this work was to investigate the biosorption performance of unmodified and Cetylpyridinium chloride (CPC)-modified biomass of Penicillium YW 01 for Acid Blue 25 (AB 25). Maximum biosorption capacity of AB 25 onto CPC-modified biosorbent was 118.48 mg g−1 under phosphoric–phosphate buffer with initial dye concentration of 200 mg L−1 at 30 °C. The biosorption pattern of AB 25 onto unmodified biosorbent in aqueous solution and phosphoric–phosphate buffer was well fitted with both Langmuir and Freundlich isotherm models. While the equilibrium data of CPC-modified biosorbent in aqueous solution and phosphoric–phosphate buffer failed to fit the Freundlich isotherm model, indicating the monolayer biosorption formed onto CPC-modified biosorbent. The values of initial biosorption rate of biosorbent in phosphoric–phosphate buffer were found to be higher than that of corresponding values in aqueous solution, indicating phosphoric–phosphate buffer enhanced the initial biosorption rate of biosorption process. Weber–Morris model analysis indicated that the boundary layer effect had more influence on the biosorption process in phosphoric–phosphate buffer. The BET surface area of CPC-modified biosorbent (0.5761 m2 g−1) was larger than that of unmodified biomass (0.3081 m2 g−1). Possible dye–biosorbent interactions were confirmed by Fourier transform infrared spectroscopy.Graphical abstractHighlights► Phosphoric-phosphate buffer improve adsorption performance of biosorbents. ► Phosphoric-phosphate buffer enhanced initial biosorption rate of biosorption process. ► The CPC-modified biosorbent was more homogenesis than that of unmodified biosorbent. ► Monolayer biosorption formed for AB 25 onto CPC-modified biosorbent. ► Effect of ionic strength was not enough to access biosorption effect in wastewater.

In this work, Trichosporon fermentans CICC 1368, which has been shown to accumulate cellular lipids efficiently using industry-agricultural wastes, was subjected to preliminary genome analysis, yielding a genome size of 31.3 million bases and 12,702 predicted protein-coding genes. Our analysis also showed a high degree of gene duplications and unique genes compared with those observed in other oleaginous yeasts, with 3–4-fold more genes related to fatty acid elongation and degradation compared with those in Rhodosporidium toruloides NP11 and Yarrowia lipolytica CLIB122. Phylogenetic analysis with other oleaginous microbes suggested that the lipogenic capacity of T. fermentans was obtained during evolution after the divergence of genera. Thus, our study provided the first draft genome and comparative analysis of T. fermentans, laying the foundation for its genetic improvement to facilitate cost-effective lipid production.

Malachite green (MG) is extensively used, although it is carcinogenic and mutagenic. In our previous study, the novel Micrococcus sp. strain BD15 was observed to efficiently decolorize MG. The aims of this study were to identify the metabolites after degradation by this strain and to identify the enzymes involved in degradation. UV–Visible, FTIR, GC–MS and LC–MS analyses were performed to determine the degradation products, and our results indicate that the intermediates of MG degradation include 4-(Dimethylamino)benzophenone, Michler's ketone, 4-(methylamino)benzophenone, 4-aminobenzophenone, 4-methylaminobenzoic acid, 4-hydroxyl-N,N-dimethylaniline, N,N-dimethylaniline, hydroxyl-4-(dimethylamino)benzophenone and 4-hydroxyl-aniline. In addition, enzyme analysis revealed that laccase and NADH-DCIP reductase are involved in the degradation of MG. To our knowledge, this is the first study of the detailed biodegradation pathway of MG by Micrococcus sp. strains.Highlights► The degradation products of MG by strain BD15 were identified. ► The possible degradation pathway of MG by strain BD15 was proposed. ► The laccase and NADH-DCIP reductase were involved in the biodegradation of MG.

Plant development is a complex process influenced by exogenous and endogenous elements. A series of postembryonic developmental events is involved to form the final architecture and contend with the changing environment. MicroRNA (miRNA) is one of endogenous non-coding RNAs, which plays an important role in plant developmental regulation. In this review, we summarized 34 miRNA families that are closely associated with plant development. Among these families, nine are expressed only in specific organs, whereas 20 families are expressed in at least two different organs. It is known that some miRNAs are expressed across most processes of plant growth, while some appear only at particular developmental stages or under special environmental conditions such as drought, waterlogging and short-day time. These miRNAs execute their diverse functions by regulating developmental gene expression levels, interacting with phytohormone signaling response, participating in the biogenesis of ta-siRNAs and affecting the production of miRNAs.

•A conception of a new-type composite is put forward.•The composite is consists of Kaolin 2.38 g/L, CaCl2 0.28 g/L, KAl(SO4)2 0.09 g/L, and EPS 1.75 mg/L.•The EPS produced by Pseudomonas aeruginosa ZJU1 plays a key role in flocculating process in the composite.•The composite has a high flocculating efficiency in removal of Microcystis aeruginosa.A novel composite consisting of clay, bioflocculant, and inorganic flocculant was designed, and its flocculating effect on harmful algal blooms (HABs) was studied in this study. The extracellular polymeric substances (EPS), produced with a yield of 3.58 ± 0.11 g/L by a newly isolated Pseudomonas aeruginosa ZJU1, was indicated to be a key component in the composite. The components and functional groups of the EPS were analyzed, and it showed that polysaccharides, proteins, and nucleic acids are the main components; polar functional groups in the EPS are responsible for its flocculating activity. The novel composite was optimized by the response surface methodology and after optimization, the optical components and contents of the composite were Kaolin 2.38 g/L, CaCl2 0.28 g/L, KAl(SO4)2 0.09 g/L, and EPS 1.75 mg/L. The flocculating rates of the composite were tested, and it could rapidly reach 100 ± 0.13% within 2 min when OD680 of Microcystis aeruginosa was 0.1; it could reach 100 ± 0.08% within 5 min for OD680 of M. aeruginosa in HABs up to 1.0. These results suggest that the novel composite will be a highly efficient material for the treatment of HABs caused by M. aeruginosa.

•Eleven mutants with different novel disulfide bridges were constructed.•Mutant DS255 exhibited significantly enhanced stability.•Engineered disulfide bonds led to increase in ΔG* and decrease in ΔS* of DS255.Rational design was applied to glucose 1-dehydrogenase (LsGDH) from Lysinibacillus sphaericus G10 to improve its thermal stability by introduction of disulfide bridges between subunits. One out of the eleven mutants, designated as DS255, displayed significantly enhanced thermal stability with considerable soluble expression and high specific activity. It was extremely stable at pH ranging from 4.5 to 10.5, as it retained nearly 100% activity after incubating at different buffers for 1 h. Mutant DS255 also exhibited high thermostability, having a half-life of 9900 min at 50 °C, which was 1868-fold as that of its wild type. Moreover, both of the increased free energy of denaturation and decreased entropy of denaturation of DS255 suggested that the enzyme structure was stabilized by the engineered disulfide bonds. On account of its robust stability, mutant DS255 would be a competitive candidate in practical applications of chiral chemicals synthesis, biofuel cells and glucose biosensors.