Dishisha Tarek, Pyo Sang-Hyun, Hatti-Kaul Rajni
Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, 221 00, Lund, Sweden.
Department of Microbiology and Immunology, Faculty of Pharmacy, Beni-Suef University, 62511, Beni-Suef, Egypt.
Microb Cell Fact. 2015 Dec 21;14:200. doi: 10.1186/s12934-015-0388-0.
3-Hydroxypropionic acid (3HP) and acrylic acid (AA) are industrially important platform- and secondary chemical, respectively. Their production from renewable resources by environment-friendly processes is desirable. In the present study, both chemicals were almost quantitatively produced from biodiesel-derived glycerol by an integrated process involving microbial and chemical catalysis.
Glycerol was initially converted in a fed-batch mode of operation to equimolar quantities of 3HP and 1,3-propanediol (1,3PDO) under anaerobic conditions using resting cells of Lactobacillus reuteri as a biocatalyst. The feeding rate of glycerol was controlled at 62.5 mg/g(CDW).h which is half the maximum metabolic flux of glycerol to 3HP and 1,3PDO through the L. reuteri propanediol-utilization (pdu) pathway to prevent accumulation of the inhibitory intermediate, 3-hydroxypronionaldehyde (3HPA). Subsequently, the cell-free supernatant containing the mixture of 3HP and 1,3PDO was subjected to selective oxidation under aerobic conditions using resting cells of Gluconobacter oxydans where 1,3PDO was quantitatively converted to 3HP in a batch system. The optimum conditions for the bioconversion were 10 g/L substrate and 5.2 g/L cell dry weight. Higher substrate concentrations led to enzyme inhibition and incomplete conversion. The resulting solution of 3HP was dehydrated to AA over titanium dioxide (TiO2) at 230 °C with a yield of >95%.
The present study represents the first report on an integrated process for production of acrylic acid at high purity and -yield from glycerol through 3HP as intermediate without any purification step. The proposed process could have potential for industrial production of 3HP and AA after further optimization. Graphical abstract Integrated three-step process for conversion of biodiesel glycerol to 3-hydroxypropionic acid (3HP) and acrylic acid (AA). Glycerol was initially converted to equimolar quantities of 3HP and 1,3-propanediol (1,3PDO) using resting cells of Lactobacillus reuteri. Subsequently, the cell-free supernatant containing the mixture of 3HP and 1,3PDO was subjected to selective oxidation using resting cells of Gluconobacter oxydans where 1,3PDO was quantitatively converted to 3HP. The resulting solution of 3HP was dehydrated to AA over titanium dioxide (TiO2) at 230 °C.
3-羟基丙酸（3HP）和丙烯酸（AA）分别是具有重要工业价值的平台化学品和二级化学品。期望通过环境友好的工艺从可再生资源生产它们。在本研究中，通过微生物和化学催化相结合的工艺，几乎定量地从生物柴油衍生的甘油中生产出这两种化学品。
使用罗伊氏乳杆菌的静息细胞作为生物催化剂，在厌氧条件下，甘油最初以补料分批操作模式转化为等摩尔量的3HP和1,3-丙二醇（1,3PDO）。甘油的进料速率控制在62.5 mg/g（细胞干重）·h，这是甘油通过罗伊氏乳杆菌丙二醇利用（pdu）途径转化为3HP和1,3PDO的最大代谢通量的一半，以防止抑制性中间体3-羟基丙醛（3HPA）的积累。随后，含有3HP和1,3PDO混合物的无细胞上清液在有氧条件下使用氧化葡萄糖酸杆菌的静息细胞进行选择性氧化，在分批系统中1,3PDO被定量转化为3HP。生物转化的最佳条件是底物浓度为10 g/L，细胞干重为5.2 g/L。较高的底物浓度会导致酶抑制和不完全转化。所得的3HP溶液在230℃下于二氧化钛（TiO₂）上脱水生成AA，产率>95%。
本研究首次报道了一种以3HP为中间体，无需任何纯化步骤，从甘油中高纯度、高产率生产丙烯酸的集成工艺。所提出的工艺在进一步优化后可能具有工业生产3HP和AA的潜力。图形摘要 生物柴油甘油转化为3-羟基丙酸（3HP）和丙烯酸（AA）的集成三步工艺。甘油最初使用罗伊氏乳杆菌的静息细胞转化为等摩尔量的3HP和1,3-丙二醇（1,3PDO）。随后，含有3HP和1,3PDO混合物的无细胞上清液使用氧化葡萄糖酸杆菌的静息细胞进行选择性氧化，其中1,3PDO被定量转化为3HP。所得的3HP溶液在230℃下于二氧化钛（TiO₂）上脱水生成AA。
