Isolation and characterization of Listeria monocytogenes in Chinese food obtained from the central area of China

The objective of this study was to investigate the prevalence and characteristics of Listeria monocytogenes isolated from Chinese food, including frozen dumplings, flavored raw meat, roasted meat, braised meat, and a cold vegetable dish with sauce. A total of 900 food samples were collected from supermarkets, open-air markets, and delicatessens in three large cities in the central area of China to examine the presence of L. monocytogenes; 21 (2.3%) of the samples were positive for this pathogen. Among the different samples, braised meat showed the highest L. monocytogenes detection rate (4.4%). Samples obtained from delicatessens showed a much higher L. monocytogenes contamination rate (8.3%) than those from open-air markets (6.7%) or supermarkets (0%). Multilocus sequence typing (MLST) analysis indicated that the 21 bacterial isolates belonged to 12 ST subgroups. ST5 was the largest and contained 7 isolates (33.3%); it was followed by ST474, ST121 and ST9 (each containing 2 isolates [10.5%]). Antibiotic susceptibility analysis showed that the 21 L. monocytogenes isolates were thoroughly resistant to cefoxitin but highly susceptible to doxycycline and ciprofloxacin. The presence of 10 virulence genes was evaluated by PCR, which showed that inlA, inlC, inlJ, prfA, hlyA, and plcB were present in all isolates and that inlB, actA, plcA and iap were present in 71.4–90.5% of the isolates. This study provides a useful reference for risk assessment and control of L. monocytogenes contamination in Chinese food and for the treatment of clinical listeriosis.     

Antifungal activity mode of Aspergillus ochraceus by bacillomycin D and its inhibition of ochratoxin A (OTA) production in food samples

The inhibition effects of bacillomycin D on the growth of Aspergillus ochraceus and the production of ochratoxin A (OTA) in food samples were investigated. The mycelia growth and sporulation were completely inhibited by 30 μg/mL of bacillomycin D. Microscopic morphological changes such as the distortion of hyphae and the disruption of spores at 20 μg/mL of bacillomycin D were significantly observed. The use of bacillomycin D resulted in cell damage, nucleic acids and proteins divulge, and more production of reactive oxygen species (ROS), and all these factors actively contributed to the promotion of apoptosis of A. ochraceus. In addition, 90 μg/g of bacillomycin D completely inhibited the growth of A. ochraceus and the production of OTA in food samples. Our results suggested that bacillomycin D showed a significant antifungal activity against A. ochraceus that could be used as a potential natural antimicrobial to control food contamination and ensure food safety.     

Intelligent release of cinnamon oil from engineered proteoliposome via stimulation of Bacillus cereus protease

Inspired by the hydrolysis of casein by protease, a new approach to deliver antimicrobials against bacterial infections was developed in this study. As a natural antibacterial agent, cinnamon oil was encapsulated into engineered liposomes inlaid with casein. The average particle size of proteoliposomes was 615.0 nm and their entrapment efficiency (EE) was 40.0%. In this work, Bacillus cereus (B. cereus) was chosen as model bacterium. The controlled release of liposome-encapsulated cinnamon oil was realized via bacterial protease secreted from B. cereus. As a result, 99.99% of the bacteria could be efficiently inhibited in rice and wheat flour.     

Screening of microbes for lipases specific for saturated medium and long-chain fatty acids of milk fat

Over 250 microbial strains were screened for lipase activity specific towards saturated medium and long-chain fatty acids. Strains showing trimyristin (C14:0) hydrolysis on agar medium were further streaked on tricaprylin (C8:0) and on olive oil (mostly C18:1) agar to identify strains hydrolysing C12–C15 fatty acids with modest or no activity towards short-chain and unsaturated fatty acids. The twenty strains showing the desired specificity were grown as liquid cultures and analysed for p-nitrophenyl (p-NP) myristate hydrolysis in the presence of Triton X-100. Cells from the cultures showing the highest activity towards p-NP myristate were analysed for specificity towards p-NP esters of different fatty acid chain lengths. On the basis of the p-NP ester profiling, four lipase samples were selected for hydrolysis experiments on butter oil. Of these, the sample obtained from the cultivation of Didpodascus capitatus met the screening criteria: C12:0–C16:0 specificity and no preference towards C18:0 and C18:1 fatty acids.     

Lime mud from paper-making process addition to food waste synergistically enhances hydrogen fermentation performance

The effect of lime mud from paper-making process (LMP) addition on the H₂ fermentation of food waste (FW) was investigated. It was found that a slight addition of LMP (1.0–4.0 g in 200 g FW) significantly enhanced the H₂ fermentation performance, not only increasing the total amount of H₂ produced but also accelerating the whole reaction, shortening the lag period, and increasing the H₂ production rate. Fermentation stability and microbial germination were also facilitated by LMP addition. This was attributed to the existence of Ca, Fe, Mn and alkaline substances such as CaCO₃ and NaOH. The batch process treating a mixture of FW and LMP was showed that the highest hydrogen production of 137.6 mL H₂/g VS was achieved at final pH 5.0, adding 3 g LMP (in 200 g FW) to the fermentation process, which lag-phase time was about 2.5 h.     

Pellicle formation,microbial succession and lactic acid utilisation during the aerobic deteriorating process of Sichuan pickle

The pellicles formation, microbial changes and lactic acid utilisation during the aerobic deterioration of Sichuan pickle were discussed in this study. By plate counting, chemical detection and HPLC analysis, the aerobic deterioration of Sichuan pickle was featured by microbial growth, pellicle formation, lactic acid decrease and pH elevation. Bacteria dominated in pellicles and the pellicles present morphological change from smooth to wrinkly along with the aerobic deteriorating process. Nine species of bacteria were identified and responsible for the pellicle formation. Combined with Lactobacillus plantarum, eight pellicle‐forming bacteria were the dominant lactic acid consuming organisms in deteriorating Sichuan pickle. Especially under the harsh acid condition of the early deteriorating period, Lb. plantarum, pellicle‐forming bacteria Bacillus amyloliquefaciens, B. subtilis and Citrobacter freundii participated in the pellicles, utilised lactic acid and increased the brine pH effectively. Sequence analysis of 16S rDNA libraries suggested that the resulting pH of 4.8–5.0 initiated the growth of more undesirable organisms, and the pellicle bacterial diversity changed greatly compared with that in the early deteriorating period. The study indicated the important role of pellicles in the initiation of Sichuan pickle's aerobic deterioration and enhanced our ability to understand and potentially control the aerobic deterioration.     

Reinforcement of polyurethane composites with an organically modified montmorillonite

A clay with reactive activity prepared by treatment of natural montmorillonite with Methylene-bis-ortho-chloroaniline (MOCA) was incorporated into polyurethane matrix and a series of PU/clay nanocomposites were obtained by in situ polymerization. The microstructure of the nanocomposites with different content of the clay was examined by atomic force microscopy (AFM). The thermal and mechanical properties of the nanocomposites with different organic clay content were characterized by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). It was found that the moduli and thermal stability of the nanocomposites were improved with augment of clay, especially, for the PU/9 wt% MO-MMT nanocomposite, compared to pure PU, the storage modulus and the loss modulus were increased by about 300% and 667% at −45 °C, respectively.     

5种香蕉果肉多酚的抗氧化活性和抑制α-葡萄糖苷酶活性

目的：比较不同品种香蕉果肉多酚的活性差异。方法：超声萃取5种香蕉果肉多酚，利用超高效液相色谱分析酚类组成，分析其抗氧化能力和对α-葡萄糖苷酶活性的抑制能力。结果：5种香蕉果肉间的多酚含量、黄酮含量和单宁含量差异显著（P＜0.05）；在5种香蕉果肉中检测出8种主要单体酚，包括4种酚酸及其衍生物和4种黄酮类化合物；5种香蕉果肉多酚具有一定的DPPH自由基清除能力、ABTS自由基清除能力和铁离子还原能力，均能抑制α-葡萄糖苷酶活性，主要活性成分芦丁、儿茶素与抑制能力呈显著正相关（P＜0.05）。南角42号香蕉果肉多酚的抗氧化能力和抑制α-葡萄糖苷酶活性的能力最强，通过混合型抑制的方式抑制酶活，其与α-葡萄糖苷酶的相互作用为放热反应。结论：香蕉果肉多酚具有很好的抗氧化能力和对α-葡萄糖苷酶活性的抑制能力，有望成为良好的α-葡萄糖苷酶选择性抑制剂。     

Fungal fucoidanase production by solid-state fermentation in a rotating drum bioreactor using algal biomass as substrate

Fucoidanase enzymes able to degrade fucoidan were produced by solid-state fermentation (SSF). The fermentation assays were initially carried out in a laboratory-scale rotating drum bioreactor, and two fungal strains (Aspergillus niger PSH and Mucor sp. 3P) and three algal substrates (untreated, autohydrolyzed, and microwave processed seaweed Fucus vesiculosus) were evaluated. Additionally, fermentations were carried out under rotational (10 rpm) and static conditions in order to determine the effect of the agitation on the enzyme production. Agitated experiments showed advantages in the induction of the enzyme when compared to the static ones. The conditions that promoted the maximum fucoidanase activity (3.82 U L^?1) consisted in using Mucor sp. 3P as fungal strain, autohydrolyzed alga as substrate, and the rotational system. Such conditions were subsequently used in a 10 times larger scale rotating drum bioreactor. In this step, the effect of controlling the substrate moisture during the enzyme production by SSF was investigated. Moreover, assays combining the algal substrate with an inert support (synthetic fiber) were also carried out. Fermentation of the autohydrolyzed alga with the moisture content maintained at 80% during the fermentation with Mucor sp. 3P gave the highest enzyme activity (9.62 U L^?1).