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化学-生物法催化生物质合成糠胺

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2019/10/18 14:32:19  

摘要:糠醛(Furfural,FAL)是从木质纤维素中提取的一种有前途且可再生的生物质平台化合物,可以进一步转化为生物燃料和生物化学品。糠胺(Furfurylamine,FLA)是糠醛的一种衍生物,它是一种重要的中间体,可用来合成生物聚合物和具有药理活性的化合物。传统合成糠胺的方法中,呋喃反应条件复杂且易生成副产物,因此更加温和安全的生物催化法将会是生产糠胺的首选。生物酶法合成工艺具有反应条件温和、对环境友好、选择性高等优点,符合“绿色化学”的要求,因此受到广泛关注。本研究尝试利用固体酸催化剂SO42-/SnO2-SEP和生物催化剂重组E. coli CV-2018全细胞串联催化方法将生物质高效转化为糠胺。研究结果如下:

首先,以具有独特孔隙结构的海泡石(SEP)为载体,与SnCl4·5H2O制备新型固体酸催化剂SO42-/SnO2-SEP。通过扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)和拉曼光谱对制备的SO42-/SnO2-SEP进行表征。发现制备的SO42-/SnO2-SEP没有改变其本身主要性质,但其比表面积增大,增加了与底物接触面积从而提高催化效率。然后,利用酸化的固体酸催化剂SO42-/SnO2-SEP (3.6 wt%)在170 oC条件下转化玉米芯30 min糠醛产率可达到37.5%。可见,该固体酸催化剂可高效催化生物质合成糠醛。

其次,将制备的糠醛溶液通过E. coli CV-2018全细胞生物催化合成糠胺。为了有效地合成糠胺,研究了各种参数的影响,得到了最佳反应条件:异丙胺与底物浓度比为3:1,反应温度为35 oC,反应pH为7.5。此外,金属离子Mg2+ (1 mM)和表面活性剂PEG-4000 (1 mM)对催化反应有很大的促进作用。通过E. coli CV-2018全细胞将制备的糠醛溶液在最佳条件下反应72 h后获得了87.3%的糠胺产率。因此,由玉米芯制备糠胺的产率为0.07g糠胺/g玉米芯,验证了化学-酶法催化生物质转化为糠胺路线的可行性。

然后,尝试构建了水-有机溶剂两相体系催化玉米芯合成糠胺。为了有效地合成糠胺,研究了各种参数的影响,最适反应体系为:水-γ-戊内酯两相体系,γ-戊内酯与水的比例为2:8 (v/v)。在两相体系中通过酸化的SO42-/SnO2-SEP (3.6wt%)催化剂转化玉米芯制备糠醛,在170 oC反应30min后糠醛产率达到49.1%,比水相体系产率增加约12%。随后将制备的糠醛溶液在两相体系中通过E. coli CV-2018全细胞生物转化为糠胺,反应56 h后糠胺产率达到71.6%。因此,由玉米芯制备糠胺的产率为0.08 g糠胺/g玉米芯,对单纯的水相体系相比,催化效率更高。

最后,选取了5种易得的生物质(例如, 玉米芯、玉米秸秆、稻杆、冬笋皮和芦苇叶)分别在两相体系中进行化学-酶法合成糠胺。研究结果表明玉米芯、冬笋皮、稻杆三种生物质所含半纤维素含量较高,制备糠醛的浓度分别95.0 mM、70.6 mM和60.3mM,产率分别达到49.1%、41.0%和35.4%。将制备的糠醛溶液通过E. coli CV-2018在两相体系下催化转化成糠胺,反应56 h后糠胺产率分别是71.6%、80.1%和88.2%。研究表明三种生物质衍生的糠醛溶液都能通过化学-酶法高效地转化为糠胺,验证了以生物质来源制备糠胺路线的可行性。

总之,本研究构建了一种利用固体酸催化剂SO42-/SnO2-SEP和生物催化剂E. coli CV-2018细胞串联催化方法将生物质有效转化为糠胺的路线,为绿色生产糠胺提供了一条新思路。

Furfural (FAL) is a promising renewableplatform compound derived from lignocellulosic biomass that can be furtherconverted to biofuels and biochemicals. Furfurylamine (FLA) is a derivative ofFAL, FLA has many applications as monomers in biopolymer synthesis and for thepreparation of pharmacologically active compounds. Preparation of FLA viatraditional synthetic routes is not straightforward due to by-product formationand sensitivity of the furan ring to reaction conditions. Therefore, a mild andsafe process will be the first choice for the production of FLA. The enzymaticsynthesis process has received extensive attentions due to its mild conditions,environmentally friendly feature, high selectivity, which are consistent withthe requirements of "Green Chemistry". In this study, tandemcatalysis with solid acid catalyst SO42-/SnO2-SEP and recombinant E. coliCV-2018 whole-cell was attempted to convert biomass into FLA efficiently. Theresults were obtained as follows:

Firstly, a novel solid acid catalystSO42-/SnO2-SEP was prepared from SnCl4·5H2O and sepiolite (SEP) with uniquepore structure. The prepared SO42-/SnO2-SEP was characterized by scanningelectron microscope (SEM),Fourier transform infraredspectrums (FT-IR), X-ray diffraction (XRD), and Raman spectra. It was foundthat the sepiolite loaded with SnCl4 had no change in its own properties, butits specific surface area was increased, and the contact area with thesubstrate was increased to improve the catalytic efficiency. Furthermore, FALwas obtained from corncob by acidified solid acid catalyst SO42-/SnO2-SEP , theyield of FAL reached 37.5% at 170oC for 30 min. Therefore,FAL could be systhetized efficiently via the catalysis of solid acidcatalyst from biomass.

Secondly, the prepared FAL liquor was convertedto FLA by E. coli CV-2018 whole cell. To effectively synthesize FLA, theinfluences of various parameters were investigated, the optimum reactionconditions were obtained as follows: the concentration ratio of isopropylamineto substrate was 3:1, the reaction temperature was 35 oC, and reaction pH was7.5. In addition, the addition of the metal ion Mg2+ (1 mM) and the surfactantPEG-4000 (1 mM) greatly promoted the catalytic reaction. Furthermore, theprepared FAL liquor biologically converted by E. coli CV-2018 whole cells toFLA at 87.3% yield within 72 h. The FLA yield was obtained at 0.07 g FLA/gcorncob. which demonstrated the feasibility of chemo-enzymatic catalyzedprocess to obtain FLA from corncob.

Thirdly, an organic-aqueous biphasic systemwas constructed for enhancing the biocatalytic efficiency. To effectivelysynthesize FLA, the influences of various parameters were investigated. Theoptimum reaction media was water-γ-valerolactone system, the phase volumetricratio of γ-valerolactone phase versus water phase was 2:8. A higher FAL yieldof 49.1% was achieved from the corncob under optimal conditions. Furthermore,when the prepared furfural liquor was used in the biotransformation reaction byE. coli CV-2018 whole cells, the FLA yield reached 71.6% at 56 h. The FLA yieldwas obtained at 0.08 g FLA/g corncob. Compared to the aqueous phase system, thebiphasic system was more efficient in this process.

Finally, five kinds of available biomasses(corncob, corn stover, rice straw, winter bamboo shoots and reed leaves) wereselected for chemo-enzymatic systheis to FLA in biphasic system. The resultsshowed that corncob, bamboo shoot shell and straw and contained higher contentof hemicellulose. The concentrations of prepared FAL from three biomass were95.0 mM, 70.6 mM and 60.3 mM respectively, and the yield of FAL rearched 49.1%,41.0% and 35.4% respectively. The prepared FAL liquor was used in thebiotransformation reaction by E. coli CV-2018 whole cells in biphasic system.It was found that FLA obtained at 71.6%, 80.1% and 88.2% yield after thebiotransformation of FAL for 56 h respectively.

关键词:玉米芯;SO42-/SnO2-SEP;糠醛;E.coliCV-2018;糠胺

Corncob; SO42-/SnO2-SEP; Furfural; E. coliCV-2018;

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