聚糖内切酶EGⅢ的克隆及其在酵母中的表达

[目的]构建可降解纤维类固体废弃物的工程菌.[方法]采用RT-PER方法克隆了绿色木霉(Trichoderma viride)AS313711的葡聚糖内切酶Ⅲ(EGⅢ)的cDNA,测序后构建到酵母表达载体pESP-2上,并通过电击法将其转到酵母感受态细胞中去,得到酵母表达转化子.通过DNS法测定该转化子在不同温度、不同pH值下酶活力的大小.[结果]EGⅢ的cDNA开放阅读框长度为1 257 bp,编码418个氨基酸,推测蛋白质分子量为44.1×103.在pH值为4.9、温度在60℃条件下,EGⅢ酶活力最高,相对酶活为100%.[结论]获得了高表达效率的EGⅢ-T-pESP-2酵母表达载体,其表达活性要比天然的酶高出3～5倍,只要调节好温度、pH值的关系,可提高纤维素葡聚糖内切酶的下游转化纤维素效率,在大规模生产中生产出大量的葡萄糖.     

红发夫酵母有机硒最佳转化条件的研究

[目的]优化红发夫酵母(Phaffia rhodozyma)有机硒转化条件。[方法]通过正交试验研究硒添加量、培养时间和装液量对红发夫酵母富硒的影响。[结果]红发夫酵母富硒的最适培养基为PDA培养基,亚硒酸钠的添加方式为分2次添加,在硒添加量20 mg/L、培养时间30 h、装液量80 m L/500 m L的条件下,红发夫酵母的生物量达10.62 g/L,有机硒转化率达63.2%。[结论]研究结果为红发夫酵母富硒的进一步研究提供了参考。     

基于农户调查的迁西县退耕还林可持续性研究

退耕还林工程实施后,其可持续性成为社会广泛关注的问题。以迁西县为例,对退耕还林的可持续性进行了研究。分别从粮食产量、土地利用及农业产业结构调整、农民经济收入、社会安全状况、退耕农民的思想观念变化等方面对迁西县退耕还林的可持续性进行了分析。得出迁西县在实施退耕还林工程后并未影响其粮食安全,土地利用及农业产业结构调整也较为合理,农民经济收入也保持了高速稳定的增长,农民思想观念亦有了很大转变,社会安全状况也可处于稳定状态,其毁林复耕的可能性极小。通过退耕还林工程的实施,迁西县基本达到了生态、经济和社会的可持续发展。     

天然复合矿物对肉猪生长性能,胴体品质影响的试验研究

９２头仔猪，分两批（每批４组）作基础日粮添加不同配方（Ａ、Ｂ、Ｃ）天然坚合矿物粉试验。结果表明，添加天然复合矿物粉对肉猪的生长性能及胴体品质均有一定的促进作用。其中以Ｂ方较稳定，日增重平均提高８．４％，料肉比下降９．２％，胴体瘦肉率提高５．０２百分点     

Converting to organic dairy farming: Consequences for production, somatic cell scores and calving interval of first parity Holstein cows

This paper aims to describe the changes prompted by conversion to organic farming for milk production and fertility of first parity Holstein cows.

Data was collected for Dutch organic farms, with a distinction made between long-standing-organic farms, converted organic farms and a reference group of conventional farms. The percentage Holstein blood in the herds, milk production (kg milk, % milk fat, % milk protein), somatic cell scores (SCS), calving interval (CI) and age at first calving (AFC) were described over time. An animal model was used to estimate the effects of conversion on different traits based on data from converted organic farms.

Milk production was lower and somatic cell counts were higher on long-standing-organic farms than on conventional and converted organic farms. Interestingly, at pre-organic farms, i.e. before their conversion, the milk production level was already lower than at conventional farms.

The estimates from our statistical analysis showed a highly significant decrease in milk yield and protein percentage due to conversion. Also fat content decreased, SCS increased and AFC increased significantly.

It can be concluded that the conversion to organic farming is a gradual process over years. Dutch farmers who decided during the late 1990s to convert to organic farming, represented a specific group of farmers distinct from conventional farmers, which was reflected by lower milk yields, milk fat percentage and protein percentage before conversion as compared to conventional farms. During conversion, significant changes in milk production, protein and fat contents and somatic cell scores took place. Age of first calving is an important difference between organic and conventional farming.     

Growth and development of bambara groundnut (Vigna subterranea) in response to soil moisture: 2. Resource capture and conversion

A study was conducted in controlled environment glasshouses to investigate the effects of soil moisture on resource capture and conversion of three landraces (DipC, S19-3 and UN from Botswana, Namibia and Swaziland, respectively) of bambara groundnut (Vigna subterranea (L.) Verdc.). The study was conducted under two soil moisture treatments: an irrigated control and a drought treatment where irrigation was withheld from approximately flowering to final harvest. Drought reduced the mean fractional intercepted radiation (f) from 0.8 to less than 0.7 across landraces. The mean light extinction coefficient (=0.46) was not affected either by landrace or watering regime, while cumulative intercepted radiation (S_ci) reduced under drought because of the reduction in f. Drought reduced total transpiration (E_c) only in DipC while it had no effect on the other two landraces. Crops under irrigation extracted most of the water from the top 50 cm of the profile while those under drought extracted water down to 90 cm. The conversion coefficient for intercepted radiation (_s; g MJ⁻¹) was reduced by 32%, from 1.51 to 1.02 g MJ⁻¹. Similarly, drought reduced the dry matter/transpired water ratio (ε_w; g kg⁻¹) by 20% from 2.05 to 1.65 g kg⁻¹.     

城乡交错区农地城市流转管理控制目标的设定

城乡交错区农地城市流转的管理控制目标是:流转效益的最优化,即流转后经济价值、生态价值和社会价值能够达到或者接近最优化;通过流转使土地资源配置合理;土地流转收益分配合理。对流转前后土地经济效益、生态效益和社会效益的价值变化都提出了评估的思路和方法。     

泵及装置原型与模型水力特性换算方法

对国内外多种泵及装置原型、模型水力特性换算方法研究所取得的进展进行了回顾,主要内容包括具有奠基意义的Moody效率换算公式,考虑比尺效应的原型、模型泵及装置效率的换算方法,以及原型、模型泵能量性能参数的换算方法。详细介绍了我国学者在这方面的研究成果,并对现有不同换算方法进行了简要的评述,指出缺乏高精度完整可靠的水泵装置原型测试数据,是目前制约水力特性换算方法深入研究的重要原因,将数值模拟与理论分析和试验研究相结合,可望取得突破性的进展。     

树立“饲草就是粮食”理念，大力发展饲草产业

饲草是草食动物的重要口粮。大力发展优质饲草产业，通过以草増粮、以草节粮、以草代粮等技术途径，可以扩大饲草来源、增加饲草产量、加大动物应用，实现化草为粮，为保障国家粮食安全和全方位夯实粮食安全根基作出重要贡献。