不同蛋白酶水解模拟餐厨垃圾优化工艺研究

[目的]研究不同蛋白酶水解模拟餐厨垃圾的优化工艺。[方法]通过单因素试验,用牛肉模拟餐厨垃圾,研究了木瓜蛋白酶、中性蛋白酶、碱性蛋白酶、胰蛋白酶和胃蛋白酶水解牛肉的优化工艺。[结果]较其他几种酶,胰蛋白酶水解效果最好,水解度最大可达到74.18%。胰蛋白酶水解的最适条件:酶用量2%,pH 7.5,固液比为1∶60,水解时间2 h,水解温度50℃。[结论]该研究为解决餐厨垃圾的同源性污染问题打下了基础。     

转TrxS基因对啤酒大麦种子贮藏蛋白含量的影响

为探讨导入TrxS基因对大麦籽粒氮代谢的作用,以转TrxS基因啤酒大麦纯合株系为材料,分析了TrxS基因的导入对大麦籽粒蛋白酶活性、醇溶蛋白和谷蛋白含量的影响.结果表明,转基因大麦籽粒的蛋白酶活性增加,发芽第3～5 d转基因大麦种子的蛋白酶活性分别比对照增加42.86%、19.35%和25.76%;发芽第2～4 d醇溶蛋白和谷蛋白的降解平均比对照下降快5.92% 和7.10%.     

蛋白酶和益生菌复合制剂对白羽肉鸡生长性能、养分利用率和粪便有害气体排放的影响

本试验旨在研究饲粮中添加蛋白酶和益生菌复合制剂对白羽肉鸡生长性能、养分利用率和粪便有害气体排放的影响.试验选取体重接近、健康的1日龄爱拔益加(AA)肉仔鸡192只,按照体重随机分为2组,每组8个重复,每个重复12只鸡.对照组饲喂基础饲粮,试验组饲喂添加蛋白酶、枯草芽孢杆菌、地衣芽孢杆菌、凝结芽孢杆菌、酵母菌复合制剂的基...     

Disentangling thermal acclimation and substrate limitation effects on C and N cycling in peatlands

Temperature and substrate availability are among the key factors controlling microbial metabolism. The relative importance of these two drivers on soil organic matter turnover is, however, hotly debated. In this study, we investigated the effect of temperature changes on the potential enzyme activities involved in C (phenol-oxidase) and N (protease and amidase) cycling by incubating peat soils collected in winter and summer at the two typical temperatures recorded in the field during these two distinct periods (4 and 19 °C, respectively). In addition, to evaluate the effect of substrate limitations, we also compared the respiration rates of the thermally adapted soils with and without plant litter additions. Results showed that both collection season and incubation temperature had a significant effect on the two enzymes involved in N-cycling, with summer and increasing temperatures having detrimental effects on the potential activities of protease and amidase, whereas none of these factors affected phenol-oxidase activity. Furthermore, while adding readily decomposable substrate accelerated decomposition rates, CO₂ flux rates were similar for all temperature conditions. Interestingly, the greatest contribution of litter to CO₂ emissions occurred in the summer samples incubated at the lower temperature, whereas for the winter samples the stimulating effect on soil respiration was observed under warmer conditions. These findings suggest that the responses of soil microbial communities to temperature and substrate availability seem to strongly depend on the long-term temperature conditions and its interaction with substrate availability.     

Influence of pea root traits modulating soil bioavailable C and N effects upon ammonification activity

Plant functional traits are useful tools for understanding plant impacts on soil nitrogen (N) mineralization. The objective of this study was to examine the root traits that govern the influence of Pisum sativum L. on potential protease and ammonification activities, which are two key microbial activities involved in N mineralization. Ammonification activity was greater during pea reproductive than vegetative stages, whereas potential protease activity did not vary along pea development. Ammonification activity was more strongly affected by root architecture traits (total root length and percentage of fine roots) than by root growth traits (root dry matter content). Pea root traits appear to affect ammonification activity in a complex manner involving variations in rhizodeposition that modulate carbon and N availability for soil microorganisms.     

Differences in the functionality and characterization of kafirins extracted from decorticated sorghum flour or gluten meal treated with protease

Kafirins have been extracted from several types of sorghums due to their potential use for production of gluten-free products. Nevertheless, the extraction of these proteins from wet-milled sorghum gluten meal (SGM) has not yet been explored. In this study, we investigated the differences in composition, color, molecular structures, functionality and in vitro protein digestibility of kafirin extracts obtained from dry-milled flour or SGM obtained from decorticated white sorghum treated with and without endopeptidic protease. Kafirins were extracted using aqueous ethanol and metabisulfite. Kafirin extracts from SGM presented higher protein purity (95% vs 86%), lower fat content (0.7% vs 2.0%), in vitro protein digestibility (89% vs 85%), and better water holding (2.8 vs 1.9 g/g) and fat absorption capacities (2.4 vs 1.6 g/g) compared to extracts from ground decorticated sorghum. Color was not affected by treatments. SDS-PAGE showed differences in the low molecular weight patterns of kafirin extracts obtained from SGM whereas FTIR analyses showed reduction of α-helical and β-turn percentages and β-sheet increment after extraction. The proposed protease treatment increased free amino nitrogen and emulsifying index of kafirins, but did not affect other functional properties. Thus, SGM represents a potential new feedstock for the extraction of food-grade kafirins.     

Role of PAR-2 in tryptase mediated IEC-6 cell injury

AIM: To investigate the role of protease activated receptor-2 (PAR-2) in the process of tryptase mediated IEC-6 cell injury. METHODS: The rat intestinal epithelial cell line IEC-6 was treated with tryptase at different concentrations (1 μg/L, 10 μg/L, 100 μg/L and 1 000 μg/L) in the presence or absence of PAR-2 antagonist FSLLRY-NH2 for 12 h respectively. The cell survival rate was detected by MTT assay. The protein levels of PAR-2 and cleaved-caspase 3 were determined by Western blotting. The LDH activity was also measured. RESULTS: Compared with control group, the cell survival rates were significantly decreased in 100 μg/L and 1 000 μg/L tryptase treated groups, the LDH activities were significantly increased in 10 μg/L to 1 000 μg/L tryptase treated groups, and the protein levels of PAR-2 and cleaved caspase 3 were significantly increased in 100 μg/L and 1 000 μg/L tryptase treated groups (P<0.05). Compared with 1 000 μg/L tryptase treated group, the LDH activity and cleaved caspase 3 protein level were dramatically decreased while the survival rate was significantly increased in the presence of PAR-2 antagonist FSLLRY-NH2 (P<0.05). CONCLUSION: Tryptase induces IEC-6 cell injury in a dose-dependent manner by activating PAR-2.     

Water-manure interactions on ammonia volatilization

The effects of imazethapyr, an imidazolinone derivative on the soil microbial biomass was investigated in a clay loam soil. Imazethapyr was applied in a field trial at the recommended field rate for soybean weeding, 50 g a.i. ha^-1. In laboratory experiments the herbicide was incorporated at the field rate and 10-fold and 100-fold higher. In both the field trials and the laboratory experiments, the field rate of imazethapyr had no adverse effects on the microbiological processes tested. But at 10-fold and 100-fold higher rates, the herbicide decreased the biomass-C content and dehydrogenase activity and increased the hydrolytic capacity and protease and catalase activity. These findings suggest that there may be a risk in monocultural practices that require repeated herbicide treatments.Research supported by National Research Council of Italy, Special Project RAISA, Subproject no. 2, Paper no. 1105     

Interrelationship between extracellular enzyme activity,ATP content,total counts of bacteria and CO2 evolution

Summary In an incubation experiment, soil was amended to induce changes in microbial growth and enzyme production. The soluble fraction of newly produced protease (extracellular enzyme) was separated from the soil by a sterilized millipore filter. The activity of total and soluble protease, ATP content, number of acridine orange-stained bacteria, and CO₂ evolution in soils were measured during the incubation. Increases in soluble and total protease activities in soils amended with agar and glucose coincided with increases in ATP content, total counts of bacteria, growth of fungi, and CO₂ evolution. In amended soils, the activity of soluble extracellular protease was about 30% of the total protease activity. Soluble extracellular protease activity was highly correlated with total protease activity (r=0.78, P<0.01), ATP content (r=0.74, P<0.01), and total counts of bacteria (r=0.94, P<0.01) during the first 6 days of incubation. Hence measurement of microbial biomass appeared to be an index for the level of extracellular enzymes in soil.     

Enzyme inhibitors in tuber crops and their thermal stability

Tubers of Cassava (Manihot esculenta), yams (Dioscorea esculenta),aroids (Amorphophallus campanulatus, Colocasia esculenta, Xanthosoma sagittifolium) and Coleus (Solenostemon rotundifolius) were screened for inhibitory activities against amylase, trypsin and chymotrypsin. Coleus tuber possessed the highest anti-amylase activity, whereas Colocasia tuber was the most potent source of anti-tryptic and anti-chymotryptic activity. Xanthosoma tubers exhibited amylase inhibitory activity and Amorphophallus tubers antiprotease activity. Dioscorea esculenta had low levels of amylase and chymotrypsin inhibitors, while Cassava tubers were totally free of inhibitors. When tubers were processed by pressure cooking, there was significant reduction/complete elimination in inhibitory activity. Partial retention of inhibition was observed in the case of amylase inhibitor in Dioscorea, chymotrypsin inhibitor in Colocasia and trypsin inhibitor in Colocasia, Coleus and Amorphophallus. In vitro experiments on heat stability of the different inhibitors revealed almost similar pattern of inactivation.