基于宏基因组学技术分析不同贮藏条件下鲶鱼片中的菌相变化

【目的】分析鲶鱼肉片贮藏过程中微生物多样性和菌群动态变化,探究天然保鲜剂对鲶鱼肉片菌相及菌落组成的影响。【方法】试验分8组,即新鲜鲶鱼片(CK0);空气包装(air-package,AP)鲶鱼片低温贮藏(4±1)℃第4、7天(AP4和AP7)样品;气调包装(modified atmosphere package,MAP,60%CO_2/40%N_2)鲶鱼片冰温贮藏(-0.7±0.02℃)第10、30天(MAP10和MAP30)样品;添加5%天然保鲜液(由壳聚糖、蜂胶、溶菌酶、Nisin和茶多酚复配而成)MAP鲶鱼片冰温贮藏第10、30和40天(MAPP10、MAPP30和MAPP40)样品。采用宏基因组学技术,测定并分析不同贮藏方式鲶鱼片全部微生物的16S r DNA序列,比较各组菌群的物种组成和丰度信息,通过Alpha多样性分析和主成分分析,考察包装方式、贮藏温度和天然保鲜液对微生物的抑制作用。【结果】8组样品中454焦磷酸测序共鉴定出25个门、433个属的细菌。MAP10、MAPP10、MAPP30中的最优势菌属和CK0一致,均为Actinomyces;而AP4和AP7中的最优势菌分别为Aeromonas(70.49%)和Pseudomonas(59.01%)。从微生物角度来看,MAP+冰温贮藏优于AP+冷藏。随着贮藏时间的延长,气调包装中的Lactococcus丰度由15.78%(MAP10)急剧上升为82.85%(MAP30)。添加天然保鲜液的MAPP10和MAPP30中Lactococcus几乎检测不到。【结论】气调包装协同冰温贮藏显著降低了鲶鱼片中细菌菌群的丰度和多样性,有利于延长鲶鱼肉的保质期。天然保鲜液中的茶多酚、Nisin和壳聚糖等能显著抑制MAP+冰温贮藏的鲶鱼片中的主要腐败菌属Lactococcus的生长繁殖。     

Methane production from thermophilic co‐digestion of dairy manure and waste milk obtained from therapeutically treated cows

Methane production from co‐digestion of dairy manure and waste milk, milk from cows treated with antibiotics for mastitis, was tested in a 2 × 4 factorial design. Four different waste milk percentages (w/w): 0% (SM), 10% (SMWM10), 20% (SMWM20) and 30% (SMWM30), were tested with two slurry percentages (w/w): 50% (A) and 25% (B) and the rest being manure at 55°C for 12 days in batch digesters. The results analyzed using a Gompertz model showed SMWM10 produced the highest methane production potential (P_m)/g volatile solids added followed by SM in both A and B. This P_m of SMWM10 in A and B was statistically non‐significant (P > 0.05). More than 96% of cefazolin‐resistant bacteria and 100% of multi‐drug‐resistant bacteria reductions were observed in all the treatments. Inclusion of waste milk at 10% in single stage digester enhances the methane production from dairy manure and could offer added benefit of waste milk treatment and disposal.     

Investigation of lactic acid bacterial strains for meat fermentation and the product's antioxidant and angiotensin‐I‐converting‐enzyme inhibitory activities

In the lactic acid bacteria (LAB) strains screened from our LAB collection, Lactobacillus (L.) sakei strain no. 23 and L. curvatus strain no. 28 degraded meat protein and tolerated salt and nitrite in vitro. Fermented sausages inoculated strains no. 23 and no. 28 showed not only favorable increases in viable LAB counts and reduced pH, but also the degradation of meat protein. The sausages fermented with these strains showed significantly higher antioxidant activity than those without LAB or fermented by each LAB type strain. Angiotensin‐I‐converting‐enzyme (ACE) inhibitory activity was also significantly higher in the sausages fermented with strain no. 23 than in those fermented with the type strain. Higher ACE inhibitory activity was also observed in the sausages fermented with strain no. 28, but did not differ significantly from those with the type strain. An analysis of the proteolysis and degradation products formed by each LAB in sausages suggested that those bioactivities yielded fermentation products such as peptides. Therefore, LAB starters that can adequately ferment meat, such as strains no. 23 and no. 28, should contribute to the production of bioactive compounds in meat products.     

Effect of grape pomace on fermentation quality and aerobic stability of sweet sorghum silage

The objective of this study was to evaluate the effect of grape pomace (GP) with different adding levels (0%, 5%, 10% and 15%, fresh matter basis), alone (GP‐LAB) or in combine with an inoculant LAB (GP+LAB), on the fermentation quality and aerobic stability of sweet sorghum silage. After 90 days of ensiling in vacuumized mini‐silos, silages were subject to a 7‐day aerobic stability test, in which chemical, microbial and polyphenol composition were measured. In the GP‐LAB group, adding GP decreased (P < 0.05) concentrations of water‐soluble carbohydrate (WSC) and butyric acid in silage. In the GP+LAB group, adding GP increased (P < 0.05) concentrations of lactic acid, WSC and crude protein, decreased (P < 0.05) final pH value, NH₃‐N ratio and butyric acid concentration in silage. Polyphenol level was reduced (P < 0.05) after silage fermentation. During aerobic exposure, the fungi count, pH value and silage temperature increased (P < 0.05), the levels of lactic acid, acetic acid and polyphenols (quercetin 3‐O‐glucoside and quercetin 3‐O‐glucuronid) decreased (P < 0.05) in silage. GP+LAB treated silage had a lag phase for aerobic spoilage. When the fermentation products, microbial counts, chemical and polyphenol composition were considered, the use of 10% GP+LAB at ensiling could provide a valuable source for improved fermentation quality and aerobic stability of sweet sorghum silage.     

原料乳中耐冷菌群及其产酶特点

耐冷菌及其分泌的耐热酶是原料乳中常见污染物,会导致乳制品腐败。通过16S rRNA基因测序分析了分离自上海地区原料乳的耐冷菌群,以及通过平板法研究不同耐冷菌的蛋白酶和脂肪酶活力。结果表明:所有的分离株属于9个菌纲,含33个菌属,其中数量占主要的菌属是假单胞菌(Pseudomonas)(55％)、不动杆菌(Acinetobacter)(10％)和黄杆菌(Flavobacterium)(5％),其余30个菌属占所有菌株数的30％。耐冷菌产酶能力平板法实验显示,大部分的耐冷菌都有产蛋白酶或脂肪酶的能力,不同菌属之间产酶特点存在差异。假单胞菌和黄杆菌主要表现为产蛋白酶活性,克雷伯氏菌(Klebsiella)主要表现为产脂肪酶活性,而大多数的不动杆菌没有产蛋白酶或脂肪酶活性。     

植物乳杆菌对致病性肠炎沙门氏菌感染蛋鸡的生产性能及其蛋、粪含菌量的影响

试验旨在研究植物乳杆菌（Lactobacillus plantarum,LP）对致病性肠炎沙门氏菌（Salmonella enteric,SE）感染蛋鸡的生产性能和鸡蛋、粪中病菌残留的影响。选用144只50周龄农大3号蛋鸡,分4个组,每组4个重复,每个重复9只鸡。空白对照组和阳性对照组饲喂基础日粮;土霉素组在基础日粮中添加5 mg/kg土霉素;乳杆菌组在基础日粮中添加10⁹ CFU/kg植物乳杆菌。阳性对照组、土霉素组和乳杆菌组蛋鸡在试验第22和24天口腔接种1 mL沙门氏菌（10⁹CFU/mL）,试验期50 d。结果显示：攻毒前,各组生产性能指标无显著差异（P>0.05）;攻毒后,与空白对照组相比,感染前期阳性对照组平均蛋重显著降低（P < 0.05）,料蛋比显著升高（P < 0.05）,鸡蛋中沙门氏菌带菌率和粪中沙门氏菌含菌量显著升高（P < 0.05）。与阳性对照组相比,感染前期土霉素组和乳杆菌组蛋鸡平均蛋重分别提高5.43%（P < 0.05）、9.64%（P < 0.05）,料蛋比分别降低11.51%（P < 0.05）、5.16%（P > 0.05）;感染后期乳杆菌组料蛋比降低9.96%（P < 0.05）,乳杆菌组鸡蛋中沙门氏菌带菌率和粪中沙门氏菌含菌量分别比阳性对照组降低43.17%、23.93%（P < 0.05）。空白对照组、乳杆菌组和土霉素组间生产性能和鸡蛋大肠杆菌、沙门氏菌带菌率均无显著差异（P > 0.05）。以上结果表明,日粮中添加植物乳杆菌和土霉素均可改善沙门氏菌感染蛋鸡的生产性能,降低鸡蛋和粪中的沙门氏菌含量,提高家禽抗感染能力。植物乳杆菌具有无污染、无残留的特点,可作为家禽养殖中理想的抗生素替代品。     

Productive performance of weanling piglets was improved by administration of a mixture of bacteriophages,targeted to control Coliforms and Clostridium spp. shedding in a challenging environment

This study was conducted to investigate the effects of bacteriophages in different environments on growth performance, digestibility, ileal and caecal microbiota, gut morphology and immunity of weanling pigs. Two hundred piglets were randomly assigned to four treatment groups with five replicate pens with 10 pigs per pen. A 2 × 2 factorial arrangement of treatments was used to investigate the response of weanling pigs to supplemental bacteriophages (0 and 1.0 g/kg of diet) in contaminated or hygienic environments. Bacteriophages supplementation did not affect average daily gain (ADG), average daily feed intake (ADFI) and gain:feed in phases I and III; however, there was a significant improvement in ADG and gain:feed in phase II. The supplementation of bacteriophages increased the overall gain:feed of pigs. The overall result showed a greater ADG and ADFI in hygienic room. There were reductions in population of both ileal (p < 0.05) and caecal (p < 0.01) Clostridium spp. and ileal coliforms (p < 0.01) with the inclusion of bacteriophages in the diet. Bacteriophages increased ileal Lactobacillus and caecal Bifidobacterium and tended to increase ileal Bifidobacterium (p = 0.08). Contaminated environment decreased ileal Lactobacillus and caecal Bifidobacterium and tended to increase ileal Clostridium (p = 0.08) and coliforms (p = 0.08). Total anaerobic bacteria was tended to decrease (p = 0.06) in contaminated environment. Jejunal villus height increased in pigs received bacteriophages, but they did not affect other morphological items. The interaction between bacteriophages and environment tended to be significant (p = 0.06) for ileal villus height and ileal villus height to crypt depth ratio. The overall faecal score was significantly greater in hygienic environment and bacteriophages groups. The present findings indicate that there is an interactive effect on feed efficiency between bacteriophages and contaminated environment. In addition, bacteriophages improve jejunum morphology, and intestinal microbiota of pigs.     

大豆根际促生菌的分离筛选及其对大豆和百脉根生长与品质的影响

从贵州毕节地区大豆根际土壤中分离溶磷菌株,从大豆根瘤中分离根瘤菌株。对分离出的溶磷圈直径与菌落直径的比值(D/d值)在2.20以上的溶磷菌株分别进行溶磷能力、生长素(IAA)及有机酸分泌能力、产酸产碱性能测定,筛选出优良溶磷菌4株;对分离出的根瘤菌通过大豆试管苗回接及促生效应试验,筛选出高效根瘤菌2株。将筛选出的6株菌经拮抗反应试验后分别按单一溶磷菌接种剂、单一根瘤菌接种剂、溶磷菌+根瘤菌复合接种剂3种处理制备菌悬液,采用盆栽方法分别对大豆和百脉根进行促生效应试验。结果表明,与对照相比,除单一根瘤接种剂对增加大豆株高无效果外,另外2个处理对大豆株高有提升效果,所有处理对大豆茎粗、生物量、结荚数、荚重、单粒数及单粒重都有明显的促进作用。其中溶磷菌+根瘤菌复合菌液对大豆株高、茎粗、幼苗地上生物量和地下生物量的促进效果最好,分别比对照高出21.26%,40.79%,15.88%和42.19%。3个处理对百脉根的第一、二茬株高及地上生物量、全氮、全磷和粗蛋白含量均有明显的提升效应,其中依然是溶磷菌+根瘤菌复合菌液的处理效果最好,分别比对照高出20.82%,54.88%,106.14%,148.78%,19.34%,61.88%和19.34%,与对照差异均达极显著水平(P<0.01)。说明所筛选的菌株组合能产生良好的促生互作效应。     

无机磷溶解菌的分离筛选及其对扁穗雀麦生长的影响

对扁穗雀麦根际溶磷微生物进行分离筛选,测定其溶磷、分泌IAA能力及对扁穗雀麦的促生效果。结果表明,不同菌株对不同无机磷底物具有选择性,以磷酸钙为磷源时,筛选的溶磷菌株都有溶磷活性,其中Br17的溶磷活性最高;以磷酸铝为磷源时,只有Br1、Br7与Br8具有溶磷活性,其中Br7溶磷活性最高。IAA测定结果显示Br4、Br8、Br17与Br24具有较强IAA分泌能力,添加生长素前体物质色氨酸时菌株分泌IAA能力增强。对培养基pH分析发现,筛选的8株溶磷菌株都为产酸型微生物。将纯化后的溶磷菌接种到扁穗雀麦无菌苗,对根长、根数、株高以及生物产量等性状考察发现接种Br8、Br13、Br17与Br24菌株对扁穗雀麦的根系影响较大,主要表现为主根变短,根数变多。接种Br7、Br8、Br13与Br24菌株促进扁穗雀麦株高增高、产量增加。综合分析,Br24在贵州地区的应用潜力最大。