毕赤酵母全细胞催化合成新型高倍甜味剂莱鲍迪苷A

本研究构建经密码子优化后的UDP-糖基转移酶UGT76G1和蔗糖合成酶AtSUS基因的重组毕赤酵母菌株GS115/p PIC9KUGT/p PICZA-At SUS,实现双酶在毕赤酵母中的胞内共表达。利用共表达菌株作为全细胞催化剂在体外进行催化反应,可成功将ST转化为RA,并在此基础上对其最适反应温度、反应p H、底物UDP浓度与底物蔗糖浓度条件进行优化。重组菌株经甲醇诱导,对不同发酵时间菌体的催化能力进行探究,确定发酵120 h菌体催化能力最佳,RA产量为0.58 mg/mL。对共表达菌株催化体系中全细胞催化条件进行优化,优化后的催化体系为:反应pH 7.0,UDP浓度1 mM,蔗糖浓度70 mM,MgCl_2浓度3 mM,ST浓度10 mg/mL,将OD_(600)为30的细胞与上述体系混合后在最适温度45℃下,200 r/min反应15 h,重组菌可将10 mg/mL ST转化为7.46 mg/mL RA,为RA酶法生物合成及其产业化应用提供技术支持。     

Biochemical effects of administering shock loads of sucrose to a laboratory-scale anaerobic (UASB) effluent treatment plant

An experimental study was undertaken to determine the effects of administering shock loads of sucrose to a laboratory-scale anaerobic effluent treatment plant (UASB reactor) treating diluted landfill leachate. Administration of shock loads of 10 g l⁻ sucrose caused accumulations of up to 7 g l⁻¹ of l-lactate and the resultant acidity caused the pH value of the reactor effluent to drop from 7.2 to 4.7 which inhibited methanogenesis.Major disturbances in the composition of the biogas also occurred and, under the severest conditions, the biogas contained up to 30% (v/v) hydrogen.     

对氯甲基苯乙烯-马来酸酐接枝蔗糖共聚物减水剂的制备

以过氧化苯甲酰（BPO）为引发剂,对氯甲基苯乙烯、马来酸酐（MAH）为聚合单体,采用非均相聚合方法,合成对氯甲基化苯乙烯-马来酸酐共聚物,并通过与蔗糖反应合成苯乙烯-马来酸酐接枝蔗糖共聚物（SP）。通过红外光谱（FI-IR）和核磁共振氢谱（1H NMR）对减水剂结构进行表征。并以净浆流动度为指标设计正交试验,考察了取代反应的反应温度、反应时间和催化剂用量等工艺条件对SP净浆流动度的影响。结果表明：当取代反应的反应温度为45℃,反应时间为2h,催化剂用量为10%时所得制品的减水性能最佳。以正交试验最佳取代反应条件得到的SP,具有良好分散性,在掺量为0.3%时,净浆流动度为320mm,减水率为27.9%。     

构建高效糖配体再生重组菌生物催化合成莱鲍迪苷D

利用拟南芥(Arabidopsis thaliana)蔗糖合酶AtSUS3构建活化糖配体尿苷二磷酸葡萄糖(uridine diphosphate glucose,UDPG)再生体系,与高效催化莱鲍迪苷D(rebaudioside D,RD)合成的糖基转移酶协同偶联完成RD的高效生物催化。从拟南芥cDNA克隆获得AtSUS3基因,将其装配至pET28a获得表达质粒pLW105,随后pLW105与携带糖基转移酶EUGT11基因的质粒共转化大肠杆菌BL21(DE3)构建双酶共表达工程菌。在不添加UDPG或者尿核苷二磷酸(uridine diphosphate,UDP)的条件下,以上述双酶共表达工程菌全细胞催化莱鲍迪苷A(RA)获得的底物摩尔转化率大于80%,RD产量达到930 mg/L。随后构建双酶基因串连质粒pLW108及双酶共表达大肠杆菌BL21(DE3)工程菌。用串连质粒构建的工程菌催化效果与双质粒共转化相同。采用共表达双酶工程菌的发酵破碎粗酶进行催化,结果显示以粗酶催化可简化催化体系,并可将细胞催化体系所需高质量浓度蔗糖用量降至质量浓度5 g/100 mL,同时在不添加外源UDPG的条件下实现RD的高效生物催化,RA底物摩尔转化率达到93%,RD产量约为1 051 mg/L。     

复合脂肪替代品的制备及理化性质研究

以蔗糖聚酯和海藻酸钠为主要原料制备一种复合脂肪替代品,在单因素实验的基础上,通过正交实验确定了其最优生产工艺,并对复合脂肪替代品的理化性质进行了测定。结果表明:最优生产工艺为蔗糖聚酯与海藻酸钠质量比2∶1、p H 4.5、搅拌温度45℃,在此条件下复合脂肪替代品的得率为6.04%。产品的外观类似油脂,在持水性、持油性、乳化性、乳化稳定性、流变性等方面均表现出较理想的功能特性。     

Development of templated carbon by carbonisation of sucrose–zeolite composite for hydrogen storage

The templated carbons were synthesised by carbonisation of a zeolite–sucrose composite. The effects of carbonisation temperature and dwelling time on the development of pore structure of templated carbon were investigated. Various characterisation techniques were employed to investigate the structural and topographical properties of template precursor as well as synthesised carbons. The highest total surface area of 1033 m²/g and micropore area of 647 m²/g were obtained for carbon synthesised at 750°C with 3 h dwelling time. It was observed that at lower carbonisation temperature or dwelling time, the surface area and pore volume were lower, which may be attributed to incomplete carbonisation of the sucrose. At higher carbonisation temperature or dwelling time, the decrease in surface area and pore volume could be the result of collapse of the pore structure. Maximum 80% micropore area was observed for the templated carbons depending on the synthesis conditions. The hydrogen uptake of the templated carbons was measured by temperature‐programmed desorption at 1 bar pressure and different subzero temperatures. The maximum uptake (0.30 wt%) was obtained at 1 bar and ?100°C for templated carbon, having a surface area of 1033 m²/g, prepared at 750°C with 3 h dwelling time. This templated carbon had the highest total surface area as well as micropore area. Copyright © 2014 John Wiley & Sons, Ltd.