To enhance the specific endo-β-1,4-glucanase activity (EGI) of three mixed substances: Trichoderma sp. (Trichoderma reesei, Trichoderma longibrachiatum, and Trichoderma pseudokoningii), we optimized the efficiency of the encoding gene, eg1, using DNA shuffling and Saccharomyces cerevisiae INVSc1 as a host. One variant, SEGI8 (the high activity protein encoded by eg1 gene using DNA shuffling) was found through screening approximately 1000 variants. The extracellular enzyme work of SEGI8 reached its highest level when cultured for 96 h, at 50 °C and a pH of 5.6, akin to the wild types. Clone harboring of the best mutant SEGI8 (selected via first-round mutagenesis) produced 169–257% more activity than transformants with three wild-type EGIs. Mutant SEGI8 produced by the clone showed broad pH stability (5.6–6.6) while performing comparable thermotolerance (60–70 °C) compared to wild EGIs; it also showed a high homology of 95%, 96%, and 97%, identical to the EGI of T. reesei, T. longibrachiatum, and T. pseudokoningii, respectively. Analysis of the sequences indicated that four point mutations causing amino acid substitution (V10A/G100S/F192L/S318G) were replaced. The major structure of the active site in SEGI8 was comprised of loop regions, with the same location as β-helix in NTEGI (the protein encoded by eg1 genes in T. reesei). It has been suggested that the mutation S318G might affect substrate binding and improved actions based on an analysis of the predicted 3D structural-modeling of SEGI8. Overall, this novel system could facilitate cellulose activity and create a foundation for constructing an efficient cellulose degradation system.

The concentration of glucose in fruit is a key index for fruit quality. Despite the fact that there are many methods to detect glucose, finding a rapid, visual, and inexpensive method to detect glucose in fruit is still a great challenge. In this study, the concept of paper-based microfluidic device (μPAD) was extended to high-performance chemo-sensors for semi-quantitative detection of glucose in different kinds of fruit. Under optimized conditions, the results showed that the method detected glucose of different concentrations and the limit of detection (LOD) can reach 3.12 mM. In the quantifications, a good linear relationship was obtained between mean intensity and glucose concentration (5∼50 mM, R2 = 0.952). The analytical results obtained by the developed approach were in good agreement with the results by spectrophotometric method. In addition, polyethylene glycol (PEG) was added to cellulose paper surface to improve the both hydrophilic and sensing performance, indicating that the PEG-cellulose paper was superior for its rapid response for glucose. Herein, a low-cost and high sensitive μPAD sensor was exploited to assess the fruit quality and guide fruit intake for diabetes mellitus patients.

Acute hepatopancreatic necrosis disease (AHPND), also called early mortality syndrome (EMS), has caused massive economic loss in aquaculture since 2009. It was considered that the disease was caused by a novel type of Vibrio parahaemolyticus which harbors a large plasmid. Two insecticidal Photorhabdus insect-related (pir) genes were found in the plasmid. In this study, 81 isolates have been collected from a shrimp farm in Maoming, Guangdong Province, PRC. Suspected isolates were identified using 3 pairs of primer recently made public. Both the 16S rRNA gene and pir gene were sequenced. ERIC-PCR was employed for analysis of strain diversity. 12 isolates were amplified by PCR and identified as Vibrio parahaemolyticus by 16S rRNA sequence alignment. Sequence alignments of the pir gene showed few mutations in the 12 strains of V. parahaemolyticus. The 12 strains separated into 3 clusters at a cut of 90% similarity by ERIC-PCR. The virulence gene expression and toxicity profile showed differences between strains. This study generated comprehensive identification of pathogenic bacteria and microbial molecular resources, which will contribute to future research of AHPND.

A Gram-staining-positive, facultative anaerobic, motile and rod-shaped bacterium, designated GSS08T, was isolated from a windrow compost pile and characterized by means of a polyphasic approach. Growth occurred with 0–4 % (w/v) NaCl (optimum 1 %), at pH 6.5–9.5 (optimum pH 7.5) and at 20–45 °C (optimum 37 °C). Anaerobic growth occurred with anthraquinone-2,6-disulphonate, fumarate and NO3− as electron acceptor. The main respiratory quinone was MK-7. The predominant polar lipids were diphosphatidylglycerol and phosphatidylethanolamine. The major fatty acids (>5 %) were iso-C15:0 (43.1 %), anteiso-C15:0 (27.4 %) and iso-C16:0 (8.3 %). The DNA G + C content was 39.6 mol%. The phylogenetic analysis based on 16S rRNA gene sequences revealed that strain GSS08T formed a phyletic lineage with the type strain of Bacillus humi DSM 16318T with a high sequence similarity of 97.5 %, but it displayed low sequence similarity with other valid species in the genus Bacillus (<96.0 %). The DNA–DNA relatedness between strains GSS08T and B. humi DSM 16318T was 50.8 %. The results of phenotypic, chemotaxonomic and genotypic analyses clearly indicated that strain GSS08T represents a novel species, for which the name Bacillus nitroreducens sp. nov. is proposed. The type strain is GSS08T (=KCTC 33699T = MCCC 1K01091T).

•AEW ice reduced the diversity of bacterial flora and pH value in shrimp.•AEW ice displayed inhibitory activity toward cathepsin B and PPO in shrimp.•AEW ice had no adverse influences on sarcoplasmic proteins in shrimp.•AEW ice had a stronger ability to inhibit the shrinkage of muscle fibers of shrimp.Preliminary mechanism of acidic electrolyzed water (AEW) ice on improving the quality and safety of shrimp was investigated by examining the physicochemical and microbiological changes, sarcoplasmic proteins and enzymatic activities. The results showed that compared with tap water (TW) ice, AEW ice had an obvious (p < 0.05) capability in limiting the changes of pH and shrinkage of muscle fibers in shrimp. Plate count enumeration and PCR–DGGE indicated that AEW greatly inhibited growth of bacteria on shrimp. Additionally, AEW ice had no adverse effects on sarcoplasmic proteins by SDS–PAGE method. And AEW ice displayed inhibitory activity (p < 0.05) toward cathepsin B and polyphenol oxidase (PPO), although it did not present positive effects on inhibiting cathepsin D, acid phosphatase and lipase activity. Thus, this study brought new evidence to further demonstrate that AEW ice can serve as a promising technology for improving the quality of aquatic products in food industry.

•A LC–MS/MS method was developed for determination of 9 mycotoxins in seafoods.•A reliable, rapid and simple sample pretreatment method was optimized.•The approach possesses a desirable level of sensitivity, recovery and precision.•Results showed that fish and dried seafoods could be contaminated by mycotoxins.A reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for simultaneous determination of nine mycotoxins, i.e., aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), ochratoxin A (OTA), zearalenone (ZEN), T-2 toxin, HT2 toxin and deoxynivalenol (DON), in fresh fish (muscle and entrails) as well as dried seafoods. Special focus was given to sample pretreatment which is crucial for an accurate and reliable analytical method. With regards to the high complexity of the matrices, extraction solvent, time, and temperature as well as clean-up cartridges were optimized to improve extraction efficiency and reduce matrix effects. The optimum procedure included ultrasound-assisted extraction with acetonitrile/water/acetic acid (79/20/1, v/v/v) at 40 °C for 30 min, defatting with n-hexane and purification by Oasis HLB cartridges. The method was further validated by determining the linearity (R2 ≥ 0.9989), sensitivity (limit of detection ≤2 μg/kg, limit of quantitation ≤3 μg/kg), recovery (72.2–119.9%) and precision (≤18.3%) in muscle and entrails of fresh crucian carp (Carassius carassius) as well as dried fish products. The method was proven to be suitable for its intended purposes. Mycotoxins of OTA, ZEN and AFB2 have been found in fresh fish and dried seafoods for the first time.

A Cr(VI)-tolerant, Gram-staining-positive, rod-shaped, endospore-forming and facultative anaerobic bacterium, designated as GSS04T, was isolated from a heavy-metal-contaminated soil. Strain GSS04T was Cr(VI)-tolerant with a minimum inhibitory concentration of 600 mg l−1 and was capable of reducing Cr(VI) under both aerobic and anaerobic conditions. Growth occurred with presence of 0–3 % (w/v) NaCl (optimum 1 %), at pH 5.5–10.0 (optimum pH 7.0) and 15–50 °C (optimum 30–37 °C). The main respiratory quinone was MK-7 and the major fatty acids were anteiso-C15:0 and iso-C15:0. The DNA G+C content was 41.1 mol%. The predominant polar lipid was diphosphatidylglycerol. Based on 16S rRNA gene sequence similarity, the closest phylogenetic relative was Bacillus shackletonii DSM 18868T (97.6 %). The DNA–DNA hybridization between GSS04T and its closest relatives revealed low relatedness (<70 %). The results of phenotypic, chemotaxonomic and genotypic analyses clearly indicated that strain GSS04T represents a novel species of the genus Bacillus, for which the name Bacillus dabaoshanensis sp. nov. is proposed. The type strain is GSS04T (=CCTCC AB 2013260T = KCTC 33191T).

Electrolyzed water ice is a relatively new concept developed in food industry in recent years. The effect of acidic electrolyzed water (AEW) ice on preserving the quality of shrimp (Litopenaeus vannamei) was investigated. Physical, chemical, and microbiological changes of the shrimp were examined during the storage. The results showed that compared with tap water (TW) ice, AEW ice displayed a potential ability in limiting the pH changes of shrimp flesh and significantly (p < 0.05) retarded the changes of color difference and the formation of total volatile basic nitrogen (TVBN). And AEW ice treatment had no adverse effects on the firmness of shrimp. Conventional plate count enumeration and PCR-DGGE demonstrated that AEW ice had a capability of inhibiting growth of bacteria on raw shrimp, and the maximum reductions of population reached >1.0 log CFU/g (>90%) on the sixth day. Moreover, AEW ice was clearly more efficient in maintaining the initial attachments between muscle fibers in shrimp according to histological section analysis. On the basis of above analysis, AEW ice can be a new alternative of traditional sanitizer to better preserve the quality of seafood in the future.

•First assessed forming-process of Vibrio parahaemolyticus biofilm at various temperatures.•25 °C is more favorable for biofilm formation than 15 °C and 37 °C.•Extensive strain variability exists during biofilm formation.•Biofilm formation was significantly influenced by strain pathogenicity.Biofilm formation is crucial for the environmental survival and transmission of Vibrio parahaemolyticus, an important food-borne pathogen in seafood. The biofilm developmental process of pathogenic (n = 22) and non-pathogenic (n = 17) V. parahaemolyticus strains on polystyrene microtiter plates under 15 °C, 25 °C and 37 °C was investigated using crystal violet staining, and validated by confocal laser scanning microscopy. The results indicated that biofilm developmental process at 15 °C and 25 °C were divergent, biofilm formation increased continuously at 15 °C, while at 25 °C biofilm formation increased gradually and peaked at 12 h. Also the biofilm formation was dramatically elevated at 25 °C in comparison with that at 15 °C and 37 °C. Additionally, pathogenic strains, on average, formed more biofilm than non-pathogenic strains at all temperatures measured. Moreover, extensive strain variability was observed during biofilm formation and indexed using the coefficient of variation (CV). This index increased with increasing temperature and this index, at all temperatures, peaked after 12 h. The results of this study provide insight into the developmental process of biofilm, which allow us to further optimize strategies to control V. parahaemolyticus biofilm in food industry.

•AEW treatment notably decreased the growth rate of V. parahaemolyticus during storage.•AEW treatment greatly extended the lag time of V. parahaemolyticus during storage.•AEW treatment accelerated the death of V. parahaemolyticus at temperatures ≤ 10 °C.•AEW treatment suppressed the proliferation of V. parahaemolyticus from real-time PCR.The objective of this study was to investigate the fate of Vibrio parahaemolyticus on shrimp after acidic electrolyzed water (AEW) treatment during storage. Shrimp, inoculated with a cocktail of four strains of V. parahaemolyticus, were stored at different temperatures (4–30 °C) after AEW treatment. Experimental data were fitted to modified Gompertz and Log-linear models. The fate of V. parahaemolyticus was determined based on the growth and survival kinetics parameters (lag time, λ; the maximum growth rate, μmax; the maximum growth concentration, D; the inactivation value, K) depending on the respective storage conditions. Moreover, real-time PCR was employed to study the population dynamics of this pathogen during the refrigeration temperature storage (10, 7, 4 °C). The results showed that AEW treatment could markedly (p < 0.05) decrease the growth rate (μmax) and extend the lag time (λ) during the post-treatment storage at 30, 25, 20 and 15 °C, while it did not present a capability to lower the maximum growth concentration (D). AEW treatment increased the sensitivity of V. parahaemolyticus to refrigeration temperatures, indicated by a higher (p < 0.05) inactivation value (K) of V. parahaemolyticus, especially for 10 °C storage. The results also revealed that AEW treatment could completely suppress the proliferation of V. parahaemolyticus in combination with refrigeration temperature. Based on above analysis, the present study demonstrates the potential of AEW in growth inhibition or death acceleration of V. parahaemolyticus on seafood, hence to greatly reduce the risk of illness caused by this pathogen during post-treatment storage.