共培养微藻Monoraphidium sp. FXY-10 与Chlorella sp. U4341提高油脂产率与沉降率

采用共培养技术,在异养条件下培养微藻Chlorella sp.U4341和Monoraphidium sp.FXY-10,提高两株微藻共培养的油脂产率;通过共培养方式促进微藻细胞的自絮凝,加速微藻细胞的沉降,以期降低微藻生物量的采收成本。结果表明:微藻Chlorella sp.U4341与Monoraphidium sp.FXY-10单独培养的油脂产率分别为272.07、268.54 mg/(L·d),而两株微藻共培养的油脂产率提高到315.60 mg/(L·d);两株微藻共培养后,自然沉降5 h,微藻细胞沉降率高于90%,远高于单独培养条件下的沉降率。因此,微藻的共培养技术有望成为解决微藻油脂产率低、采收成本高两大瓶颈问题的解决方案。     

异养小球藻油脂正己烷提取工艺优化

为确定最佳异养小球藻油脂正己烷提取工艺,对提取工艺中的关键参数如藻细胞溶液质量浓度、破碎压力、破碎次数、萃取时间、萃取温度、萃取剂正己烷添加量对油脂得率的影响进行了研究。结果表明,最佳油脂提取工艺条件为藻细胞溶液质量浓度110 g/L、破碎压力100 MPa、破碎次数4次、萃取时间5 h、萃取温度40℃、正己烷添加量9 m L/g(以藻粉干重计),在该条件下萃取5次,油脂得率最高,可以达到55%左右。     

Frequency of DLK1 c.639C>T polymorphism and the analysis of MEG3/DLK1/PEG11 cluster expression in muscle of swine raised in Poland

DLK1 — (Drosophila like element 1) is a paternally expressed gene, associated with the callipyge phenotype in sheep. In a present study we designed a new real-time PCR alleleic discrimination assay for genotyping of a silent C/T mutation (c.639C>T) in DLK1 gene in swine. The DLK1 c.639C>T mutation was highly polymorphic in all breeds analyzed and C allele was predominant in Landrace and Duroc while T allele was more frequent in Pietrain and Pu?awska breed. Moreover, we analyzed mRNA expression of DLK1 and adjacent genes — MEG3 and PEG11 in muscles of swines of different breeds raised in Poland. We did not observe significantly different expression of DLK1, MEG3 or PEG11 mRNA in any of analyzed breeds. We also attempted to assess the effect of DLK1 (c.639C>T) on the expression of genes in callipyge locus but did not find significant differences between animals with alternate genotypes (C/C and T/T homozygotes).     

2022年中国大陆食品中沙门菌耐药性特征分析

目的 了解2022年中国大陆31个省（自治区、直辖市）食品中沙门菌分离株耐药性及黏菌素可转移耐药基因mcr的携带情况。方法 采用微量肉汤稀释法测定575株食源性沙门菌对11类17种抗菌药物的敏感性,采用PCR检测受试菌株中mcr基因的携带情况,并对mcr基因PCR阳性菌株开展全基因组测序和生物信息学分析。结果 575株沙门菌中耐药菌株占比84.70%（487/575）,测试菌株对萘啶酸（NAL）耐药率最高,为58.61%（337/575）,发现耐亚胺培南（IPM）和耐替加环素（TGC）沙门菌各1株。多重耐药率达61.39%（353/575）,同时耐受抗菌药物种类最高为10类。共存在147种耐药谱,优势耐药谱为SAM-CT-AMP-NAL,占比28.57%（42/147）。不同样品来源的沙门菌耐药率差异有统计学意义,冻生鸡肉沙门菌分离株耐药率最高,为95.51%（85/89）。河北和黑龙江来源的分离株耐药率较高,均为100%。检出6株mcr-1基因阳性沙门菌,检出率为1.04%（6/575）,2株来自湖北,另外4株分别来自河北、安徽、辽宁和山东的食品样品,均为多重耐药株,主要携带aac（6''）-laa、mcr-1.1、fosA3等耐药基因,质粒复制子类型主要为IncI2、IncP1和IncHI2等。结论 2022年中国大陆食品中沙门菌分离株整体耐药水平较高,多重耐药现象严重,耐药谱复杂,存在携带mcr基因的多重耐药菌株,应该引起足够重视。     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

鸡源大肠埃希氏菌mcr-1基因携带及分析

目的 了解在农业农村部禁止使用多黏菌素作为动物促生长使用后四川部分地区鸡源大肠埃希氏菌（E.coli）mcr-1基因的携带情况,为制定进一步防控措施提供依据。方法 采集四川部分地区市场售卖点肉鸡直肠拭子,用含有多黏菌素（终浓度4 μg/mL）的EC肉汤增菌接种含多黏菌素（终浓度4 μg/mL）的麦康凯平板,挑取可疑菌落,采用PCR方法鉴定菌株并检测mcr-1基因;微量肉汤稀释法测定mcr-1基因阳性菌株对临床常见抗菌药物耐药情况。脉冲场凝胶电泳（PFGE）对mcr-1基因阳性菌株进行同源分析。耐药基因质粒结合实验验证mcr-1基因传播途径。结果 从70份肉鸡样本中的13份检出mcr-1基因阳性大肠埃希氏菌,检出率18.57%（13/70）,对实验的13种抗生素,除13株mcr-1阳性菌株对头孢西丁有12株敏感以外,对其他抗生素都表现出不同程度的耐药,其中四环素和甲氧苄啶/磺胺甲恶唑耐药率最高,达到了100%（13/13）;其次是氨苄西林和氯霉素,耐药率为84.62%（11/13）。PFGE显示13株mcr-1阳性大肠埃希氏菌分属13个不同的型别;质粒结合实验显示mcr-1基因能够通过质粒传播。结论 mcr-1基因在鸡大肠内大肠杆菌中检测率比较高,且鸡大肠中mcr-1阳性大肠埃希氏菌的耐药情况比较严重。     

Potential use of a microalga (Chlorella vulgaris) in the pigmentation of rainbow trout (Oncorhynchus mykiss) muscle

The main purpose of this work was to evaluate the colouring effect of carotenoids present in dry biomass obtained from stressed cells ofChlorella vulgaris. Total carotenoids represented only 0.2% of dry algal biomass and consisted mainly of canthaxanthin, lutein, astaxanthin and their esters. — A rainbow trout feeding trial was conducted in order to investigate the effects of dietary algal incorporation as a pigment source, in comparison to that obtained with synthetic pigments, both astaxanthin and canthaxanthin. — The colour intensities measured in muscle were compared, in each case, with those which constitute the Salmonids Roche Colour Card, and proved similar after both 3 and 6 weeks feeding, with a significant increase detected, but at the end of experiment (9 weeks) the increase was shown only in spectrophotometric (quantitative) results.Chlorella vulgaris biomass, which is storable without any special precautions, thus appears to be a promising source of carotenoids to use in commercial fish finishing diets, quite comparable in efficiency with the existing synthetic pigments. Algal biomass micronization, which was also tried out, was not found to be advantageous for the efficiency of colouring, no evidence having been found of any difference in its absorption and in the distribution of pigment through muscle, even if a 150-g rainbow trout, which has a rather short digestive tract, was used.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom

The purpose of this study was to establish the microbiological safety of salad vegetables and sauces served in kebab take-away restaurants. Comparison with published microbiological guidelines revealed that 4.7% of 1213 salad vegetable samples were of unsatisfactory microbiological quality due to Escherichia coli and/or Staphylococcus aureus levels at ≥10² cfu g⁻¹. Another 0.3% of salad samples were of unacceptable quality due to S. aureus at ≥10⁴ cfu g⁻¹ (2 samples) or the presence of Salmonella Kentucky (1 sample). Cucumber was the most contaminated salad vegetable with regards to unsatisfactory levels of E. coli (6.0%) or S. aureus (4.5%). Five percent of 1208 sauce samples were of unsatisfactory microbiological quality due to E. coli, S. aureus at ≥10² cfu g⁻¹ and/or Bacillus cereus and other Bacillus spp. at ≥10⁴ cfu g⁻¹. A further 0.6% of sauce samples were of unacceptable quality due to Bacillus spp. (Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis) at ≥10⁵ cfu g⁻¹ or the presence of Salmonella Agbeni (1 sample). More samples of chilli sauce (8.7%) were of unsatisfactory or unacceptable microbiological quality than any other sauce types. The results emphasize the need for good hygiene practices in kebab take-away restaurants handling these types of ready-to-eat products.     

Investigations of the natural microflora of poppy seeds (<Emphasis Type="Italic">Papaver somniferum</Emphasis>) and hazelnut kernels (<Emphasis Type="Italic">Corylus avellana</Emphasis>) including microbiological decomposition

Fatty seeds of Papaver somniferum and Corylus avellana undergo a rapid microbial degradation after being ground. Those bacteria and fungi which are mainly responsible for the microbial decay were identified, and the most important growth and death processes were documented using crucial indicator-organisms. Additionally, an aflatoxin-screening was carried out in order to assess the possible risk-potential of food intoxication. The acid value (indicator for free fatty acids) of poppy seeds and hazelnut kernels was determined during their fermentation in order to document the decomposition of triglycerides.In this study it could be proved that initially a natural decay of oil seeds is caused by bacteria, yeasts and mould fungi. After the bacteria died in the course of time, yeasts and mould fungi dominated the germ spectrum. Bacteria taking part in the degradation were identified as varieties of Staphylococcus xylosus, Enterobacteriaceae and coliforms. Yeasts were identified as Pichia burtonii, and the mould fungi are associated with the genus Alternaria.On account of the absence of the genus Aspergillus in the spectrum of mould fungi, no aflatoxin was produced.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Biochemical profile of halophilous microalgae strains from high-andean extreme ecosystems (NE-Chile) using methodological validation approaches

The main goal of this work is to characterize the biochemical profile of three halophilous microalgal strains isolated from extreme ecosystems in northern Chile to assess their potential as possible sources of technological and commercial advantages. A procedure for the validation of a routine method for determining the total protein, carbohydrate, lipid and chlorophyll a (Chl-a) contents in Chlorella fusca, Dunaliella salina and Spirulina sp. has been developed. Detection limits of 10.8 μg/mg, 2.7 μg/mg and 5.6 μg/mg for total protein content and 3.5 μg/mg, 1.8 μg/mg and 8.8 μg/mg for total carbohydrate content were determined in C. fusca, D. salina and Spirulina sp., respectively. Most of the biological macromolecule levels measured in the microalgae were in accordance with the magnitude of previously reported data for other strains of the same taxa. However, lower levels than expected of lipids and Chl-a were measured in C. fusca and Spirulina sp., which may be associated with an imbalance between specific growth rates and the rate of macromolecule synthesis. The protein values measured in Spirulina sp. (52.3 ± 2.2 μg/mg DW) were close to the lower limit of the range reported in the literature for non-halophilous strains of the same genus. Except for the Chl-a quantification procedure, the analytical methods for macromolecules had a high degree of repeatability and reproducibility. The variability among repeated measurements of Chl-a was associated with auto-degradation processes during pigment extraction.     

含水量对新疆鲜食核桃贮藏期黄曲霉生长及黄曲霉毒素M1积累的影响

目的:提高新疆鲜食核桃的贮藏安全性。方法:以新疆“新2”薄皮核桃为材料,无菌水接种为对照组,黄曲霉菌接种为试验组,将从自然霉变核桃上分离纯化出的黄曲霉菌人工接种至不同含水量(10%,15%,20%,25%,30%)的新疆薄皮鲜食核桃上,探究黄曲霉菌生长量及产毒变化情况。结果:最适宜黄曲霉菌生长繁殖并分泌黄曲霉毒素M₁的核桃含水量为15%;随着核桃含水量的升高,黄曲霉菌生长量呈先上升后下降趋势,但各含水量之间的生长量各不相同,且黄曲霉菌生长量与产生黄曲霉毒素M₁的量成正比。结论:原料的含水量与黄曲霉菌生长量及产生黄曲霉毒素M₁的量有着密切的关系。