纤维素酶的化学修饰

应用二环己基羰二亚胺活化海藻酸钠,然后与纤维素酶相联接.修饰后纤维素酶的性质发生了变化.其中,最适温度、最适pH均发生了变化;对pH、热稳定性有了较大程度的增强;对某些抑制剂(Hg~(2 )、Cu~(2 )、Ag~ 、Ca~(2 ))有较强的抵抗能力.     

细菌海藻酸的研究进展

海藻酸是β-D-甘露糖醛酸和α-L-古洛糖醛酸通过1-4糖苷键聚合而成的长链高分子化合物。综述了细菌海藻酸的结构、相关基因和合成过程,讨论了它的发酵生产和研究开发前景。     

海藻酸钠——明胶协同固定化红茶菌制备工艺的优化

【目的】确定海藻酸钠和明胶复合载体协同固定化红茶菌的最佳工艺条件,为红茶菌饮料实现标准化工业生产提供理论参考。【方法】以海藻酸钠—明胶协同固定化红茶菌,利用响应面分析法探讨海藻酸钠浓度、明胶浓度、CaCl2浓度对固定化红茶菌的机械强度和总糖利用率的影响。【结果】固定化颗粒的机械强度随着海藻酸钠浓度与CaCl2浓度的增加而不断增加,随着明胶浓度增加机械强度先增大后减小;固定化颗粒的总糖利用率随着明胶浓度和CaCl2浓度的增大均先增大后减小,随着海藻酸钠浓度的增加而不断减小。【结论】固定化颗粒最佳制备工艺条件为：海藻酸钠浓度5.50%、明胶浓度1.50%、氯化钙浓度0.51%,在此条件下制备的固定化颗粒的机械性能好总糖利用率较高。     

固定化漆酶对刚果红染料脱色降解的研究

[目的]探讨固定化漆酶脱色降解刚果红染料的最佳反应条件。[方法]以海藻酸钠为载体、戊二醛为交联剂,进行漆酶的固定化,并研究了固定化漆酶用量、染料浓度、反应温度和pH对染料脱色率的影响。[结果]固定化漆酶脱色降解刚果红染料的最佳条件为酶用量1 g,染料浓度40 mg/L,反应温度65℃,pH=4.5。在该条件下降解3 h,固定化漆酶对刚果红染料的脱色率达92.6%,重复利用5次后,脱色率仍能保持在50%左右。[结论]该研究为染料废水的有效处理提供了理论依据。     

Effect of dietary mannan-oligosaccharides on in vivo performance, nutrient digestibility and caecal content characteristics of growing rabbits

To evaluate the effect of mannan-oligosaccharides (MOS) on in vivo performance, nutrient digestibility, fermentation characteristics and caecal microbial populations of rabbits, 144 thirty-five days old hybrid Hyla were equally divided into three groups, one of which was fed the same diet without additives (control group), one with antibiotics (colistin sulphate, 144 mg/kg; tylosin, 100 mg/kg; oxytetracyclin, 1000 mg/kg) and one with MOS (1 g/kg of diet). Mortality rate, live weight, feed intake and feed conversion ratio were recorded up to 62 days of age. At 60 days nutrient digestibility was measured by acid insoluble ash method. The caecal content of 10 rabbits per group was collected at 62 days and analysed for volatile fatty acids production, ammonia content and microbial count. Rabbits from the control group had a significantly (p < 0.01) lower body weight at 62 days (1638.9 g vs. 1779.4 g and 1862.5 g, respectively for the control, MOS and antibiotic groups) while the antibiotic group showed a higher (p < 0.05) feed intake than the control group (127.9 g/day vs. 109.3 g/day). Rabbits from the MOS group had a higher apparent digestibility of cellulose (34.27% vs. 29.61% and 27.49%, respectively for the MOS, control and antibiotic groups) and, as a consequence a higher level of acetate in the caecal content (39.93 mmol/l vs. 34.21 mmol/l and 23.09 mmol/l, respectively for the MOS, control and antibiotic groups). Caecal microflora of the MOS group rabbits also had a higher fermentative activity in respect of protein source, as demonstrated by the higher productions of branched chain fatty acids. MOS and antibiotics significantly reduced the colonies of Coliformis (2.32 vs. 3.20 vs. 2.40 logCFU/g, respectively for the MOS, control and antibiotic groups, p < 0.01). Mannan-oligosaccharides at 1 g/kg of diet can be used as an alternative to antibiotics during the rabbit's growth period.     

Influences of increased levels of biotin, zinc or mannan-oligosaccharides in the diet on foot pad dermatitis in growing turkeys housed on dry and wet litter

Foot pad dermatitis (FPD) is very common in turkeys and it is an animal health and welfare issue affecting not only performance and walking ability but also the carcass quality. Thus, there is a great need to find out the preventive measures against this problem. The potential roles of extra dietary biotin, Zn and mannan-oligosaccharides (MOS) in preventing the development of FPD were assessed in this study which was conducted on 2-week-old female turkeys over a period of 4 weeks. The birds were allotted to four groups, with 29 each, and housed on dry wood shavings in floor pens. The turkeys were fed a control (300 μg biotin and 50 mg Zn/kg), high biotin (2000 μg/kg), high Zn (150 mg/kg) or MOS (1%) diet. Half of the turkeys in each group were additionally exposed to wet litter (27% DM) for 8 h daily in adjacent separate boxes. Foot pads of the birds were examined on days 0, 7, 14, 21 and 28 and assessed macroscopically and histopathologically for foot pad lesions. High dietary levels of biotin or Zn significantly reduced the severity of FPD on dry litter (score 1 vs. 2 in control) but not on wet litter. However, MOS did not affect the severity of foot pad lesions either on dry or wet litter. In addition, the severity was overall substantially higher on wet (approximately three times) than on dry litter. The present results suggest that adding high levels of biotin or Zn to the diet could reduce the development and severity of FPD on dry litter but without having any preventive effects on wet litter. Finally, the high litter moisture appears to be the major factor resulting in FPD. Therefore, the litter should be maintained dry to minimize the prevalence and severity of FPD in turkeys.     

肉兔日粮中添加异麦芽寡糖饲喂效果研究

选用年龄、体重相近的断奶新西兰白兔40只和加利福尼亚兔20只,分成4组,分别饲喂含异麦芽寡糖(IOS)0％(对照组)、0.15％、0.3％和喹乙醇0.01％的日粮,研究IOS对肉兔生产性能及其腹泻发病率、死亡率的影响。结果如下:①0.3％IOS组日增重分别较对照组、0.15％IOS组、 喹乙醇组降低14.44％、15.74％、17.76％(P<0.01),料肉比较对照组、喹乙醇组高20.98％、22.31%(P<0.01),较0.15％IOS组高17.15％(P<0.05)。0.15％IOS组与对照组、喹乙醇组相比,日增重、料肉比差异不显著(P>0.05)。表明0.3％IOS对肉兔生长及饲料利用均不利。②0.15％IOS组、0.3％IOS组与对照组相比,肉兔腹泻发病率分别降低50.0％、62.5％,死亡率降低66.5％、100％;与喹乙醇组相比,腹泻发病率虽高,但亦无一只因病死亡。表明添加IOS后可有效降低肉兔腹泻发病率和死亡率。③本试验结果初步表明,添加0.15％IOS对肉兔日增重、料肉比无影响,且可显著降低其腹泻发病率和死亡率,可部分替代喹乙醇使用。     

Characterization of a vector-non-transmissible isolate of Tomato spotted wilt virus

The characteristics of a thrips‐non‐transmissible isolate of Tomato spotted wilt virus (TSWV), designated TSWV‐M, were compared with those of a thrips‐transmissible isolate, designated TSWV‐T. TSWV‐M showed a narrower host range than TSWV‐T. Adult thrips failed to transmit TSWV‐M, although the vector acquired the virus during the larval stages. TSWV‐M was detected by RT‐PCR in adult thrips bodies, but not in thrips heads, suggesting that loss of thrips transmissibility was the result of the absence of virus in adult thrips salivary glands. Whereas N (nucleoprotein), NSs (non‐structural protein) and G_C (the C‐terminal portion of the glycoprotein precursor protein) were present in similar amounts in leaf tissue from TSWV‐M‐ or TSWV‐T‐infected plants, G_N (the N‐terminal portion of the glycoprotein precursor protein) was present at much lower amounts in TSWV‐M‐ than in TSWV‐T‐infected plants. SDS‐PAGE and immunoblotting analysis of TSWV‐M and TSWV‐T virion preparations with G_N‐ and G_C‐specific antibodies revealed similar amounts of the G_N and G_C glycoproteins in TSWV‐T virions, but lower amounts of G_N than G_C in TSWV‐M virions. This resulted in a statistically significant reduction in the G_N/G_C ratio in TSWV‐M virions. In affinoblots, the G_C and G_N glycoproteins of TSWV‐M exhibited weak binding with lectins showing affinity for N‐linked oligosaccharide structures. Sequence analysis of M RNA (medium segment of the TSMV genome) revealed no deletions or frameshift mutations in the G_N/G_C precursor of TSWV‐M. However, five amino acid changes were detected in the G_N/G_C precursor. A single, relatively conservative amino acid substitution (V→I) was observed in the NSm protein. Sequence analysis of S RNA (small portion of the TSMV genome) revealed a large intergenic region with no changes in the N protein and with three amino acid changes in the NSs protein.     

褐藻酸钠对白萝卜幼苗耐盐适应性的影响

采用水培的方式研究了褐藻酸钠对白萝卜幼苗遭受盐胁迫的缓解作用。结果表明，在3～12 g?L-1的氯化钠胁迫下，加入0.5 g?L-1褐藻酸钠后，白萝卜幼苗的存活率提高41.1 %，根数增加34.9 %，单株质量增加34.7 %，超氧化物歧化酶（SOD）活性增强35.4 %。褐藻酸钠可提高白萝卜幼苗的耐盐适应性，缓解氯化钠胁迫造成的伤害。     

多轮定向酶解木聚糖制备木低聚糖的研究

研究了多轮定向酶解未水解木聚糖的低聚糖组成、得率、适宜的用酶量及重复利用未水解底物的次数。结果表明 ,随着轮数的增加 ,木聚糖被降解的难度越来越大 ,而且木低聚糖的组成、平均聚合度也发生变化。采用逐步加大用酶量同时适当缩短酶解时间的方法 ,不仅能够获得较高的木低聚糖得率 ,而且可以改善酶解液的澄清度。但在实际生产中 ,重复利用未水解木聚糖的轮数应以 2～ 3轮为宜