一株具有ACC脱氨酶活性固氮菌的筛选与鉴定

ACC（1-aminocyclopropane-1-carboxylate, 1-氨基环丙烷-1-羧酸）脱氨酶是近年来发现的许多植物促生细菌（Plant growth promoting bacteria, PGPB）共有的一个特征性酶,很多具有ACC脱氨酶活性的细菌能够增强植物抗逆性,缓解干旱、淹水、盐碱、高温、病虫害等对植物的危害。因此,ACC脱氨酶阳性细菌的筛选和研究对促进农业生产具有重要意义。本文从大量样品中分离、筛选到1株ACC脱氨酶阳性固氮菌,编号为7037,该菌株ACC脱氨酶活性为-丁酮酸2.530 mol /(hmg),protein,固氮酶活性为C2H410.068 nmol /(hmg), protein;具有较为广泛的碳源利用能力和很强的环境适应能力,被鉴定为节杆菌属（Arthrobacter sp.）的一个种。盆栽试验显示,小白菜接种7037菌株比对照组鲜重增加了139%,差异极显著。该菌株可望进一步研究开发成为微生物肥料的生产菌种。     

BAF反应器中好氧反硝化细菌的筛选分离及反硝化特性研究

针对BAF反应器出水总氮浓度显著减少这一现象,以反应器中的生物膜为接种物,采用倍比稀释和酸碱指示剂培养基相结合的方法,成功筛选得到2株能有效降解硝酸盐氮的菌株N1和H1,从而证明好氧BAF反应器的生物膜中确实存在好氧反硝化细菌。经形态观察和生理生化特征分析,初步鉴定菌株N1和H1均为假单胞菌属（Pseudomonas）。菌株N1和H1好氧反硝化特性测试表明其对硝酸盐氮的反硝化作用主要发生在对数生长期。生态影响因子试验确定菌株好氧反硝化过程主要影响因素是投菌量、温度、初始pH和C/N。适宜的反硝化运行参数分别为：投菌量5%和10%,温度30℃和25℃,初始pH值6.0, C/N（摩尔比）12.0:1和4.6:1。该研究可为好氧BAF工艺短程同步硝化反硝化的设计和运行提供理论和技术支持。     

多株益生菌复合饲料发酵剂的应用效果试验

选择180头"外三元"肥育猪,分小、中、大猪三个试验组,同时饲喂3种试验日粮(即三组饲料原料的发酵产品),每种试验日粮的饲喂量分成3个水平,并以饲喂基础日粮(即全价配合饲料)为对照。饲喂45 d(正试期30 d)后,统计日增重,并屠宰大猪测定猪肉品质。结果表明:与单纯饲喂基础日粮相比,添加试验日粮Ⅰ、试验日粮Ⅱ、试验日粮Ⅲ的育肥猪的生产性能明显提高,日均增重分别提高了13.6%～17.1%(P<0.05)、1.8%～8.9%、3.5%～13.8%,肉质明显改善,猪肉滴水损失分别降低了33.72%、16.17%2、2.61%,且肌肉粗蛋白、肌肉脂肪含量有不同程度的提高。     

中国传统乳制品中优良乳酸菌的筛选及复合菌株发酵的初步研究

该试验针对中国少数民族传统乳制品,分离纯化得到56株乳酸菌。其中7株厌氧菌,11株乳球菌,38株乳杆菌。通过传代试验、凝乳时间、酸奶酸度及凝乳时风味的感官评价,选出其中4株性能较佳的乳酸菌：杆菌A、B,球菌C、D。球杆菌1∶1进行复合菌发酵性能研究,结果表明复合菌在发酵过程中,产酸速度比单菌株发酵剂快,能在5h内达到凝乳,且后酸化程度较弱,4℃保藏21d后酸度维持在120°T左右,符合工业化发酵剂的要求。通过对4种复合菌发酵剂的后酸化能力、产双乙酰能力、蛋白水解能力以及发酵乳的感官效果比较,最后筛选出AD复合菌发酵牛乳的效果最佳,具有成为生产发酵剂的潜力。     

降解纤维素菌株筛选及其鉴定

筛选高效降解纤维素菌株,为秸秆饲料的生产工艺优化奠定基础。以玉米秸秆为主要研究对象,通过降解纤维素菌株的富集培养、分离提纯及玉米秸秆的降解率和CMC酶活性测定方法,对采自新疆的26个土样在25℃±1进行富集培养30 d,初步得到能以秸秆为唯一碳源生长的34株霉菌,并对其进行分离提纯,得到14株霉菌,通过CMC酶活实验选出酶活最强的四株霉菌（M3〉M42〉M6〉M21）,并对其作出形态学初步鉴定。结果为：M6和M42属于青霉属,M3和M21属于曲霉属。试验表明筛选得到的菌株都具有较强的降解玉米秸秆所需要的酶系,并有较好的玉米秸秆生物降解的研究价值。     

Palatability and physicochemical properties of sausages prepared via lactic acid fermentation and drying at low temperature

The present study aimed to assess the palatability of sausages undergoing low‐temperature fermentation and drying process. Lactobacillus sakei D‐1001 or Lactobacillus salivarius A001 were used as starter cultures for fermentation, and the following properties of the sausages were investigated: colony‐forming units of lactic acid bacteria; concentrations of lactic acid, protein, peptides, and free amino acids; distribution of protein; composition of free amino acids; and physical properties and taste. Alterations in the composition of proteins, peptides, and free amino acids as well as in various physical properties were caused by fermentation by lactic acid bacteria. A sensory test indicated that the palatability of the fermented sausages was greater than that of the non‐fermented sausages, particularly in terms of hardness and juiciness. This was considered to be due to protein degeneration and changes in the physical properties of the sausages as a result of fermentation by lactic acid bacteria. However, the taste of the fermented sausages was sourer than that of the non‐fermented sausages, and therefore, inferior. Our study revealed that the palatability of the sausages in terms of hardness and juiciness were increased by low‐temperature fermentation by lactic acid bacteria and the drying process.     

Effect of pineapple stem starch feeding on rumen microbial fermentation,blood lipid profile,and growth performance of fattening cattle

Pineapple stem starch (PS) was evaluated for its suitability as a new starch source in concentrate for fattening cattle, based on the growth performance, blood profile, and rumen parameters of 36 steers in a 206‐day feeding study. PS was formulated as a 40% concentrate and fed with forage in comparison with ground corn (GC) and ground cassava (CA) formulated at the same level. PS feeding improved weight gain and feed conversion ratio without affecting feed intake. PS did not obviously influence blood lipid profiles throughout the experiment. Ruminal concentration of total short‐chain fatty acids (SCFA) increased with PS without affecting SCFA composition throughout the feeding study. Rumen amylolytic group, especially Ruminococcus bromii, was dominant in the rumen microbial community, and showed increased abundance by PS feeding throughout the experiment. These results clearly indicate the potential of PS as a useful starch source for fattening cattle in terms of rumen fermentation and growth performance.     

猪呼吸道疾病综合征药物防控技术研究进展

猪呼吸道疾病综合征（PRDC）在养猪业中广泛流行,发病原因复杂,由多种细菌、病毒、寄生虫及环境应激等因素共同引发,普遍造成猪生长迟缓和猪肉品质下降,还有相当比例的病猪死亡,严重影响养猪业的发展。胸膜肺炎放线杆菌（APP）、副猪嗜血杆菌（Hps）、链球菌（SS）是常见的细菌性病原,而猪繁殖与呼吸障碍综合征病毒（PRRSV）、猪圆环病毒2型（PCV2）、伪狂犬病毒（PRV）是常见的病毒性病原,合理用药防治PRDC十分关键。头孢喹肟、氟苯尼考及加米霉素等抗生素因抗菌谱广、抗菌活性强、在猪体内药代动力学特征优良等优点被广泛用于防控细菌性感染的猪呼吸道疾病。对于病毒性感染的猪呼吸道疾病,常用的抗病毒药物有细胞因子及中药,尤其是中药,不仅可以抗病毒还可增强机体免疫力,应用前景非常广阔。文章系统地阐述了上述抗菌药物的抗菌机理、药效学及药动学,详细介绍了上述抗病毒药物的抗病毒机理及其在病毒性猪呼吸道疾病上的应用,以期为合理用药防控PRDC提供一定的建议。     

抗菌肽对抗生素耐药菌株的抑菌活性研究

[目的]研究抗菌肽对抗生素耐药菌株的抑菌活性。[方法]利用抗性平板划线法从腹泻病牛血便中筛选分离出1株耐药菌,通过16S rDNA序列进行鉴定,采用琼脂孔穴扩散法通过梯度盐酸壮观霉素（spectinomycin,Spe⁺）、氨苄青霉素（ampicillin,Amp⁺）、硫酸卡那霉素（kanamycin,Kan⁺）和氯霉素（chloramphenicol,Cm⁺）试验确定该菌药敏特性,并利用1种抗菌肽制剂对该菌株进行药敏试验。[结果]经BLAST比对分析该菌16S rDNA序列,鉴定该耐药菌为科氏葡萄球菌（Staphylococcus cohnii）,此菌对Amp⁺敏感,但对试验中其他抗生素均有耐药性,各梯度抗菌肽对该耐药菌均具有明显的抑菌活性。[结论]抗菌肽能有效抑制耐药科氏葡萄球菌的生长,有望在畜牧生产中代替抗生素使用。