蛋白酶解对鲣鱼肉乳化特性的改善

天然鱼蛋白乳化性不佳,难以满足实际生产需求,但鱼蛋白的酶解改性可改善其功能特性,并拓展应用范围。以鲣鱼白色肉为原料,以水解度和乳化性为主要指标,比较了不同蛋白酶(胰蛋白酶、风味蛋白酶、木瓜蛋白酶)和水解时间对酶解液制备和鱼蛋白乳化性的影响,优化了酶解工艺参数。将鱼蛋白进行冷冻干燥后,分析鱼蛋白酶解前后溶解性、乳化性和起泡性等功能特性的差异。结果表明,当胰蛋白酶添加量2 000 U·g^-1,酶解10 min时,鱼蛋白水解度(DH)达到8.2%,此时鱼蛋白乳化特性最佳。与酶解前样品相比,酶解后鱼蛋白的乳化活性和乳化稳定性显著提高,其溶解度、起泡性和起泡稳定性均有一定程度的改善。酶解制备的鲣鱼蛋白在广泛pH范围内具有更好的功能性质,在食品工业具有更高的应用价值。     

PEDV N蛋白的原核表达纯化及B细胞抗原表位预测分析

本研究旨在对猪流行性腹泻病毒(porcine epidemic diarrhea virus,PEDV)N基因进行克隆构建、表达与其B细胞抗原表位性质的预测。将PEDV的N基因进行PCR扩增,克隆到原核表达载体pET-28a(+)中,经酶切验证获得阳性克隆,将阳性克隆在表达菌E. coli BL21(DE3)中表达。通过对表达条件及纯化条件的优化,获得高纯度表达蛋白。利用生物信息同源模型化软件Swiss-Pdb Viewer建立PEDV-N蛋白的3D结构,并根据生物信息学软件DNA-Star预测PEDV-N蛋白的二级结构、抗原性、亲水性和表面可及性分析,综合分析预测其B细胞抗原表位。经预测PEDV-N蛋白氨基酸序列中存在13个B细胞优势抗原表位区域。研究结果将进一步为PEDV-N蛋白体外表达产物的应用及研制基因工程疫苗提供理论基础。     

施钙对瘠薄红壤旱地花生土壤理化性质的影响

为探讨钙肥对瘠薄红壤旱地花生土壤理化性质影响，同时为优化花生生长环境提供理论依据，本研究在 湖南长沙选取红壤瘠薄旱地以及3个不同粒型大小花生品种（大粒湘花2008、中粒湘花55、小粒蓝山小籽），运用土 柱试验栽培法，设置施钙肥（CaO）和不施钙2个处理，对花生主要生育期的根际、0~20cm土壤理化性质进行测试与 分析。结果表明：在缺钙酸性土壤下，施钙能提高所有品种、各时期（成熟期略有不同）、各土层花生土壤的pH值， 调节土壤过酸强度；提升土壤有机质含量（蓝山小籽＞湘花2008＞湘花55）；显著增加土壤碱解氮含量（湘花55＞湘 花2008＞蓝山小籽）；更好地提高大、中粒型品种土壤有效钾含量；降低大、中粒型品种土壤有效磷含量。因此，在 氮、磷、钾营养元素充足，钙元素缺失的土壤下，增施石灰钙肥，既可降低土壤酸度，又能提高有机质、碱解氮、有效 钾含量，却降低速效磷含量，在缺钙酸性土壤花生生产中施用石灰时应增施磷肥，从而保障花生高产高效栽培。     

三江源区不同建植年限人工草地根系动态特征

根系动态特征能够反映人工草地植物利用土壤资源的效率和群落恢复演替的程度。本研究以三江源区不同建植年限（5、6、9和13年）人工草地植物根系为研究对象，利用“微根管”技术，连续两个生长季（2015年5-9月和2016年5-9月）探究了4个建植年限人工草地根系动态特征。结果表明：地上生物量和丰富度在建植5~9年呈下降趋势，建植9~13年显著上升；土壤理化性质呈“N”字型变化，不同建植年限间差异显著；随建植年限增加，根系寿命、累积生产量和累积死亡量均波动上升，根系的生长和死亡主要发生在0~10 cm土层；根系平均现存量随建植年限增加持续增加，建植6~9年趋于深层化；根系生产量、死亡量和现存量具有明显季节变化，6月为生长高峰期，7月为现存量高峰期，8月为死亡高峰期，建植9年人工草地根系正生长高峰期迟于其他建植年限；建植年限和土层深度直接影响根系寿命，其余环境因子通过影响土壤速效养分或地上生物量间接影响根系现存量。综上所述，建植人工草地能够增加地上生物量和丰富度，改善土壤质量，促进根系现存量的增加，建植6~9年人工草地的二次退化现象只是暂时性过渡阶段，可在此阶段制定合理的人工管理措施来保证土壤养分的稳定输入，加快群落正向演替的进程，从而提高人工草地的群落稳定性和恢复力。     

Characterization of Spray-Dried Hydrolyzed Proteins from Pink Perch Meat Added with Maltodextrin and Gum Arabic

In the present study, spray-dried pink perch meat protein hydrolysate (PPH) and hydrolysate with maltodextrin and gum arabic (PPHMG) were characterized in relation to their physical, rheological, functional, antioxidant, thermal, and sensory properties. The Herschel–Bulkley model was suitable to explain the flow behavior of PPH and PPHMG emulsions. Both the samples exhibited functional and antioxidant properties. Antioxidant activities were significantly higher for PPH compared with PPHMG (p<0.05). PPH and PPHMG alone did not exhibit antimicrobial activity but enhanced the activity of chitosan against pathogens. Sensory acceptability of the samples in soup revealed that PPHMG of up to 4% was highly scored without any traces of bitterness, whereas for PPH, a concentration of up to 3% was acceptable.     

Investigation of the high-amylose maize starch gelatinization behaviours in glycerol-water systems

The effect of glycerol on gelatinization behaviours of high-amylose maize starch was evaluated by confocal laser scanning microscopy (CLSM), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), texture analyzer (TPA) and rheometer. Gelatinization of the high-amylose maize starches with glycerol content of 10% (w/w) began at 95.4 °C (T_o), peaked at 110.3 °C (T_p), and completed at 118.9 °C (T_c). The birefringence began to disappear at around 100 °C and finished at 120 °C which corresponded well to the onset and conclusion temperatures obtained by DSC. The high-amylose maize starch granules maintained original morphological structure at 100 °C and swelled to a great degree at 110 °C. The high-amylose maize starch paste formed at 100 °C showed the lowest hardness (39.92 g), while at 120 and 130 °C, showed the highest hardness (610.89 g and 635.43 g, respectively). It should be noted that in going from 100 °C to 110 °C there is a significant increase in the viscosity of the slurry solution. The identical apparent viscosity was observed when the shear rate exceed 100 s⁻¹, resulting from the high-amylose maize starch granules were completely gelatinized at 120 °C, which was consistent with DSC analysis.     

Effect of germination time and temperature on the functionality and protein solubility of sorghum flour

Sorghum was germinated for different time (12, 24, 36 and 48 h) at different temperatures (25, 30 and 35 °C) and the changes in their nutritional and functional properties of germinated sorghum flour were assessed and compared with native sorghum flour. Germination inversely affects the crude protein, fat, fibre and ash content. A decrease in water absorption and swelling power and increase in oil absorption capacity was observed due to enzymatic starch modification as the germination duration progressed. Germination of sorghum increased the gel consistency while paste clarity was decreased as compared to native flour. Proteins were modified by action of enzymes during higher germination time and temperature conditions, which results in significantly higher protein solubility of germinated sorghum flour, which also result in enhancing the foaming and emulsifying properties of the flour. Lowest % synersis value and least gelation concentrations were observed in native sorghum has, which increased during germination and were highest in sorghum germinated for 48 h at 35 °C. Germination in overall can be used as low cost natural bio-processing technique for the preparation of modified flour with enhanced function properties without chemical modification or genetic engineering.     

Cattle manure and inorganic nitrogen fertilizer application effects on soil hydraulic properties and maize yield of two soils of Murewa district,Zimbabwe

This study set out to determine the effects of cattle manure and inorganic N‐fertilizer application on the hydraulic properties and maize yield of a clay and sandy soil in a smallholder farming area of Zimbabwe. Four fields classified as homefields (HF: more fertile and closer to homesteads) and outfields (OF: less fertile and further from the homesteads) were selected on clay and sandy soil. They were subjected to four treatments, control (no fertility amendment), 5, 15 and 25 t/ha cattle manure + 100 kg/ha N (as ammonium nitrate) for 7 years. A two‐way randomized complete block design was used with fertility and field type as the two factors. Clay soil hydraulic properties, which included density of macropores with a diameter >300 μm, unsaturated hydraulic conductivity, steady‐state infiltration rate, moisture retention under low suction and maize grain yield, were significantly improved (P < 0.05) by fertility management compared with the control and were generally comparable between the HF and OF. Fertility management significantly improved maize grain yield on sandy soils but did not enhance hydraulic parameters, thereby indicating poor responsiveness in structural build‐up. On the other hand, significantly different hydraulic parameters between the sandy soil HF and OF suggested effects of other factors not related to soil fertility and field type treatments. We therefore concluded that application of a high rate (25 t/ha) of cattle manure and inorganic N‐fertilizer is beneficial for fertility restoration to the degraded OFs with associated comparable hydraulic properties on HFs and OFs on clay soil, unlike on sandy soil.     

冬季室内刺参养殖水质管理方式试验

于2007年12月进行了冬季反季节养殖刺参的试验,结果表明:每天换水深度为40 cm的方式水质质量较好,是目前较可行的换水方式。     

绿色木霉Fn10-1纤维素酶的分离纯化及酶学特性测定

试验研究了绿色木霉Fn10-1纤维素酶的初步纯化及酶学性质开展研究。结果表明,该纤维素酶的最适催化温度为70℃,最适pH 7.6,在温度为4~50℃下均能保持较稳定的酶活,高于50℃以后,热稳定性变差,酶活力开始急剧下降。pH在5.6~7.6时该酶有较好的稳定性。Na+、Mn2+、Fe2+、Mg2+、Co2+、Ca2+、Ba2+、Al3+对纤维素酶具有一定的激活作用,Ag+、Fe3+、Cu2+、Zn2+、K+对该酶有一定的抑制作用,其中Cu2+的抑制作用尤为明显。