Subjects: Biology >> Bioengineering submitted time 2017-07-24 Cooperative journals: 《中国生物工程杂志》
Abstract：古紫质4(Archaerhodopsin 4, aR4)是新近发现的古生菌Halobacterium species xz515红膜上唯一的光敏视黄醛蛋白，具有和细菌视紫红质(Bacteriorhodopsin, bR)相似的质子泵功能，但在中性pH条件下，其质子释放和摄取顺序与bR相反。针对质子供体天冬氨酸97(Aspartic acid 97, D97)对aR4光循环、特别是对质子释放摄取顺序和菌株ATP生成率的影响，采用基因定点突变技术，构建了aR4的单突变体D97N，以及相对应的bR单突变体D96N。采用紫外-可见吸收光谱和闪光动力学光谱技术初步研究突变对视黄醛键合区、光反应中间态M态和O态、质子泵功能以及菌株ATP生成率的影响。结果表明，D97N突变对视黄醛紫外-可见光吸收波长没有太大影响，但造成M态衰减时间的显著延长、质子泵功能的消失以及菌株ATP的生成率大幅降低。与bR中的D96作用相比，D97对aR4质子功能的影响有所不同，这可能与D97所处的一个更为疏水性的胞外侧环境有关。
Subjects: Biology >> Bioengineering submitted time 2017-07-24 Cooperative journals: 《中国生物工程杂志》
Abstract：谷氨酰胺转胺酶（TGase）的产量不足的问题一直限制其工业化生产规模，故采用基因组重排的方法，筛选高产谷氨酰胺转胺酶菌株。通过对不同制备条件下原生质体纯度和形成率的考量，获得制备原生质体的最优条件为以6mg/mL的溶菌酶浓度进行酶解，酶解时间2h。再优化融合条件，以2min紫外灭活和40min热灭活结合的方法挑选出融合子。通过两轮基因组重排，经过96孔板发酵高通量筛选和摇瓶发酵复筛验证，获得了一株产酶达7.12U/mL的茂源链霉菌，相比最初选用菌株的平均酶活提高65.5%。发酵结果显示，酶活提高的原因可能是在重组后原酶成熟更快更彻底，且得到的菌株遗传稳定性良好。证明基因组重排能够有效提高菌株的产酶水平，同时为谷氨酰胺转胺酶产量提高提供理论依据。
Subjects: Biology >> Botany >> Plant ecology, plant geography submitted time 2016-05-03
Abstract： Aims The concentration of CO2 and other greenhouse gases in the atmosphere has considerably increased over last century and is set to rise further. Forest ecosystems play a key role in reducing CO2 concentration in the atmosphere and mitigating global climate change. Our objective is to understand carbon storage and its distribution in forest ecosystems in Zhejiang Province, China. Methods By using the 8th forest resource inventory data and 2011–2012 field investigation data, we estimated carbon storage, density and its distribution in forest ecosystems of Zhejiang Province. Important findings The carbon storage of forest ecosystems in Zhejiang Province was 602.73 Tg, of which 122.88 Tg in tree layer, 16.73 Tg in shrub-herb layer, 11.36 Tg in litter layer and 451.76 Tg in soil layer accounting for 20.39%, 2.78%, 1.88% and 74.95% of the total carbon storage, respectively. The carbon storage of mixed broadleaved forests was 138.03 Tg which ranked the largest (22.91%) among all forest types. The young and middle aged forests which accounted for 70.66% of the total carbon storage were the main body of carbon storage in Zhejiang Province. The carbon density of forest ecosystems in Zhejiang Province was 120.80 t·hm–2 and that in tree layer, shrub-herb layer, litter layer and soil layer were 24.65 t·hm–2, 3.36 t·hm–2, 2.28 t·hm–2 and 90.51 t·hm–2, respectively. The significant relationship between soil organic carbon storage and forest ecosystem carbon storage indicates that soil carbon played an important role in shaping forest ecosystem carbon density. Carbon density of tree layer increased with age in natural forests, but decreased in the order over-mature >near-mature >mature >middle-aged >young forest in plantations. The proportions of young and middle aged forests were larger than any other age classes. Thereby, the carbon storage of forest ecosystems in Zhejiang Province could be increased through a proper forest management.
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