非水相固定化生物催化的研究进展

非水相固定化生物催化技术有效拓宽了生物催化过程研究的应用范围。本文分别介绍了水-有机溶剂两相以及离子液体、超临界流体、质子惰性有机溶剂和深低共熔溶剂等新型非水相介质以及无机和高分子载体及无载体固定化技术在生物催化研究中的应用进展。展现了各种非水相介质与固定化技术对底物溶解度、酶的稳定性及产物产量等性能的促进作用,体现了其对酶活及生物催化反应的选择性等方面的不利影响,而且突出显示了非水相介质与固定化技术的结合是提高酶和微生物的活性、稳定性与选择性等性能的一个有效手段,再通过生物反应器的选择或设计以及工艺优化,有助于一些生物催化过程更高效地实现工业化。     

非水相糖苷酶高效催化的研究进展

近年来,应用糖苷酶在非水相中生物催化合成糖苷类化合物以及对糖基化合物的糖基定向改造已成为目前的一个研究热点。通过糖苷酶生物催化机理的阐述,综述了非水体系中糖苷酶催化寡糖合成与烷基糖苷合成的应用研究,尤其是耐有机溶剂糖苷酶在天然先导化合物非水相催化中的应用。非水相糖基体系为糖苷酶的高效催化及选择性催化提供了独特的环境,可望成为功能性寡糖及天然产物高效改性等领域的重要研究手段。     

非水相细胞催化研究进展

非水相细胞催化可提高水不溶化合物溶解度,改变热力学平衡以利于产物合成,是生物催化的重要组成部分。本文介绍了非水相细胞催化体系中溶剂和催化剂的筛选,如lgP值法和以产物高萃取率为目标的计算机辅助分子设计,以及催化剂的溶剂耐受性;综述了提高非水相细胞催化活性的方法,包括极端微生物的筛选和构建、细胞固定化等,以及非水相细胞催化反应在香料、药物及药物中间体等方面的应用现状;最后从生物学和工程学角度展望了非水相细胞催化研究的努力方向。     

非水相酶催化技术的研究进展

非水相酶催化技术是在传统的酶学领域上迅速发展起来的一个全新分支。介绍了非水相酶催化技术的概况、反应体系分类、非水介质中的酶学性质以及该技术最新的研究方向等。     

非水相生物酶催化在精细有机合成中的应用

非水相生物酶催化是近几年出现的一种新的生化技术，利用该技术可完成许多用传统酶催化法难以完成的化学反应。此技术的研究和开发将在精细化工领域中具有巨大的应用价值。     

两相分配生物反应器治理有机废气研究进展

通过研究国内外关于两相分配生物反应器治理有机废气进展,介绍了搅拌釜生物反应器、生物滴滤塔等多种两相分配生物反应器的结构及其工作原理;分析了硅油、十六烷等不同非水相对于不同目标污染物的去除效果;研究了两相分配生物反应器对有机废气的处理性能;最后指出如何消除液态非水相的泡沫化和反应器的堵塞问题是今后研究的关键。     

非水相中的酶催化

酶在非水相中仍具有催化活性这一发现大大扩展了酶在化工中的应用,。与在水相中进行的酶反应相比,酶在非水相中进行反应有许多优越性。本文对目前国内外有关这一领域的研究工作进行了介绍,对影响水相中酶催化的各种因素进行了讨论。     

糖苷类化合物非水相生物催化结构修饰的研究进展

介绍了非水相生物催化的现状,包括常用催化剂种类如游离酶、固定化酶和全细胞催化剂,常见的非水相催化介质如有机溶剂体系、无溶剂体系、离子液体体系以及超临界流体介质体系,阐述了糖苷类化合物的去糖基化修饰、糖基化修饰、酰化修饰以及甲基化修饰等方法,并叙述了结构修饰对化合物性质的影响,如提高化合物的溶解度、增强化合物的稳定性以及提升化合物的生物活性等,简单介绍了目前糖苷类结构修饰化合物的相关应用。     

非水相酶催化技术的应用

该项目利用非水相酶催化技术开发了光学活性环氧丙醇、手性2-辛醇、鲸蜡油、类可可酯和单酰甘油酯5个酶反应新产品,并提供了适合工业化应用的酶法生产新工艺。采用具有水解(S)-环氧丙醇丁酸酯专一性的根霉脂肪酶得到光学纯度超过95％e.e.的(R)-环氧丙醇丁酸酯;开发了固定化酶和双亲分子非共价修饰酶相协同的新方法,拆分得到的(S)-2-辛醇的光学纯度达98.0％e.e.;采用无溶剂系统,在63L反应器中进行了中试放大试验,所得鲸蜡油产品含蜡量达到95％;以资源丰富、价廉的乌桕脂为原料,利用1,3-位选择性脂肪酶和有机相中酶促反应,制得类可可脂纯度超过90％;以假单胞菌脂肪酶为催化剂进行无溶剂法棕榈油甘油解反应制得单甘酯,并在15L反应器中进行了放大试验,产品中单甘酯含量为76.0％,还对单甘酯在化妆品中的应用进行了初步研究。     

《应用生物催化》特色教学内容概览

《应用生物催化》是生物化工专业的核心课程。其研究为化学、医药、食品等领域高附加值产品的生产奠定基础。生物催化的特色教学领域包括非水相体系、手性物质合成、定向进化和极端微生物等方面。应用生物催化核心教学内容的归纳与总结,将有助于学生快速掌握本学科的知识体系,并为生物化工领域的科研人员提供重要参考资料。     

The use of CO2 for reversible pH shifting,and the removal of succinic acid in a polymer‐based two‐phase partitioning bioreactor

BACKGROUND: Succinic acid (SA) is an intermediate in the production of commodity chemicals, but SA bioproduction has not yet been commercialized due to end product inhibition and high product separation costs. Two‐phase partitioning bioreactors (TPPBs) can increase volumetric productivity through in situ product removal, although SA uptake by polymers requires a pH below the pK_A2 of SA (4.2). It was proposed to reversibly reduce the pH with CO₂ sparging for absorption of SA, followed by nitrogen stripping to allow continued bioproduction after returning to metabolic pH levels. RESULTS: At 1 atm CO₂ sparging lowered the pH of RO water to 3.8 but only to 4.75 in medium, requiring acid/base pH adjustment in subsequent experiments. Actinobacillus succinogenes was temporarily exposed to pH 4.2 for between 5 min and 4 h to observe the effect on subsequent growth; cells could grow after up to 4 h of low pH exposure, sufficient time for SA uptake. Because atmospheric CO₂ could not adequately lower the pH of medium, a TPPB was operated with the pH being shifted using strong acid/base; SA was recovered in situ, however, the accumulation of salts hindered further cell growth. CONCLUSION: Several key elements of this novel processing strategy were successfully demonstrated, and work is continuing with high pressure CO₂ to achieve the desired pH adjustment levels. Copyright © 2011 Society of Chemical Industry     

Extraction of anionic dyes with ionic liquid–nonionic surfactant aqueous two-phase system

The cloud point of nonionic surfactant (Triton X-114) in ionic liquid ([Bmim]Cl) aqueous solution exhibits as increase and then decrease and increase again with the increase of ionic liquid (IL) content, which is the origin of an IL–nonionic surfactant aqueous two-phase system. The nonionic surfactant-rich phase coexists with a high content of IL aqueous solution phase in the IL–nonionic surfactant aqueous two-phase system. The partitioning of various ionic dyes indicates that anionic species exhibit a high partitioning coefficient between the IL-rich phase and the nonionic surfactant-rich phase.     

非水相体系中海藻酸钠-壳聚糖微胶囊粒径及强度性能

固定化技术是提高生物催化剂在非水相中活性和稳定性的一种很有工业应用潜力的手段。采用乳化-内部凝胶化与络合反应制备海藻酸钠-壳聚糖(AC)微胶囊作为固定化载体,筛选5种有机溶剂构建了培养基-有机溶剂两相体系,模拟酵母细胞培养条件,将AC微胶囊在培养基-有机溶剂两相体系中振荡48 h,5种两相体系对AC微胶囊形态没有明显影响;在培养基-癸二酸二丁酯两相体系中,当壳聚糖分子量在40000～100000、成膜反应时间在2～5 min范围内变化时,分子量小(40000)和成膜时间长(5 min)的AC微胶囊粒径稳定,破碎率较低、机械强度较大,适于用作进一步非水相细胞催化的固定化载体。两相体系中AC微囊化酵母细胞活性保持良好,能实现生物转化生产。     

Continuous Countercurrent Extractive Biocatalysis in Aqueous Surfactant Two‐Phase Systems

To evaluate the possibility of performing extractive biocatalysis in continuous mode, the hydrolysis of penicillin G in a micellar solution containing the nonionic surfactant Tergitol NP‐7 was chosen as model system. While the product phenylacetic acid distributes into the micellar phase, 6‐aminopenicillanic acid moves preferably into the aqueous phase. The yield in the continuous multi‐step process was higher in comparison to equivalent batch systems. Overall, the results demonstrate the suitability of aqueous surfactant two‐phase systems for continuous biocatalytic reactive extraction processes.     

Simultaneous removal of sulfate and selenate from wastewater by process integration of an ion exchange column and upflow anaerobic sludge blanket bioreactor

The application of an integrated process configuration comprising of an ion exchange (IX) column and an upflow anaerobic sludge blanket (UASB) bioreactor for the simultaneous removal of SO₄^2- and total Se from synthetic mine wastewater was evaluated. Use of an IX column as a pre-treatment (not as post-treatment) to the UASB bioreactor gave the best overall removal performance. The combined treatment reduced the total Se and SO₄^2- concentration from 8.0 and 1441 mg/L to 0.2 and 28.0 mg/L, respectively. This study demonstrated for the first time that an IX process as a pre-treatment to a biological process can significantly improve the oxyanion removal efficiency and the overall treatment of Se-laden wastewaters.     

Reactive Separations for In Situ Product Removal of Enzymatic Reactions: A Review

The topic of integrating enzymatic reactions with in situ product removal is addressed. Different integrated reactive separations structured accordingly to the corresponding unit operations, i.e., reactive distillation, reactive chromatography, reactive crystallization, and extractive biocatalysis, are discussed. Special attention is given to their realization with homogenous and heterogeneous biocatalysis. Various enzyme immobilization techniques are presented and distinct strategies for installation of heterogeneous catalysts into process equipment are discussed.     

Enhancement of bioconversion gangliosides to monosialotetrahexosylganglioside by in situ sialic acid removal and recovery

Monosialotetrahexosylganglioside (GM1) production via bioconversion from gangliosides is promising for industrial application because it has the advantages of a high GM1 yield and an environmentally friendly process. Sialidase hydrolyzes gangliosides to GM1 producing sialic acid as a by‐product, which inhibits the sialidase activity, while the incomplete conversion of gangliosides was indicated by thin‐layer chromatography (TLC) in the presence of sialic acid. The sialic acid showed competitive inhibition on the sialidase activity with an inhibition constant of 0.75 mmol/L. By harnessing the in situ product removal (ISPR) technique, 50 g/L of crude gangliosides was completely converted to GM1 after a 12 h conversion. The GM1 concentration increased from 0.42 to 10.88 g/L in the ISPR system, which was 59.1 % higher than that of the control (6.84 g/L GM1). In addition, sialic acid was recovered simultaneously with a yield of 74.7 %. In summary, the ISPR system improved the bioconversion from gangliosides to GM1 and recovered sialic acid within a one‐step bioprocess.     

酶促反应结晶研究进展

在“双碳”背景下,绿色可持续的酶促反应正受到工业界的广泛关注,但在实际应用中仍面临着诸多挑战,如反应平衡的限制、不稳定产物的分解、酶的产物抑制等。结晶作为一种高效成熟的分离技术,可通过移除液相产物的方式有效解决上述问题。同时,结晶也是晶体产品的“生成”过程,其与酶促反应耦合可一步实现晶体产品的高效、绿色、可控制备。综述了近年来酶促反应结晶的研究进展,介绍了原位产物结晶（ISPC）技术的发展历程,并讨论了结晶与酶促反应耦合时的相互影响关系;从结晶方式和过程控制角度阐述了酶促反应结晶的实现形式和连续化过程;最后,对酶促反应结晶这一耦合过程的发展和应用进行了总结和展望。     

原位转移技术用于酵母合成2-苯乙醇

研究了酵母转化L-苯丙氨酸(Phe)合成2-苯乙醇(Pea)的常规和带原位转移的补料分批培养过程特性. 在常规培养中,以优化补料策略将糖浓度控制在0.1~0.3 g/L,使副产物乙醇浓度小于1%,而Pea的最高终浓度仅为3.85 g/L,因产物抑制效应无法获得更高浓度. 采用大孔树脂FD0816作为原位转移产物的介质,Pea最终总浓度达到12.80 g/L,平均生成速率为0.38 g/(L×h),比未添加树脂的培养体系分别提高了232%和35.7%. 采用乙醇溶液对发酵用的树脂进行动态洗脱,Pea洗脱率达到95%以上,洗脱液中Pea浓度达到60 g/L.