Lacmata Stephen Tamekou, Kuiate Jules-Roger, Ding Yamei, Xian Mo, Liu Huizhou, Boudjeko Thaddée, Feng Xinjun, Zhao Guang
CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
Laboratory of Microbiology and Antimicrobials Substances, Department of Biochemistry, Faculty of Sciences, University of Dschang, Dschang, Cameroon.
PLoS One. 2017 Mar 2;12(3):e0173150. doi: 10.1371/journal.pone.0173150. eCollection 2017.
Poly(3-hydroxypropionate) (P3HP) is a thermoplastic with great compostability and biocompatibility, and can be produced through several biosynthetic pathways, in which the glycerol pathway achieved the highest P3HP production. However, exogenous supply of vitamin B12 was required to maintain the activity of glycerol dehydratase, resulting in high production cost. To avoid the addition of VB12, we have previously constructed a P3HP biosynthetic route with β-alanine as intermediate, and the present study aimed to improve the P3HP production of this pathway. L-aspartate decarboxylase PanD was found to be the rate-limiting enzyme in the β-alanine pathway firstly. To improve the pathway efficiency, PanD was screened from four different sources (Escherichia coli, Bacillus subtilis, Pseudomonas fluorescens, and Corynebacterium glutamicum). And PanD from C. glutamicum was found to have the highest activity, the P3HP production was improved in flask cultivation with this enzyme. To further improve the production, the host strain was screened and the culture condition was optimized. Under optimal conditions, production and content of P3HP reached to 10.2 g/L and 39.1% (wt/wt [cell dry weight]) in an aerobic fed-batch fermentation. To date, this is the highest P3HP production without VB12.
聚（3-羟基丙酸酯）（P3HP）是一种具有良好可堆肥性和生物相容性的热塑性塑料，可通过多种生物合成途径生产，其中甘油途径实现了最高的P3HP产量。然而，需要外源供应维生素B12来维持甘油脱水酶的活性，导致生产成本较高。为避免添加VB12，我们之前构建了一条以β-丙氨酸为中间体的P3HP生物合成途径，本研究旨在提高该途径的P3HP产量。首先发现L-天冬氨酸脱羧酶PanD是β-丙氨酸途径中的限速酶。为提高途径效率，从四种不同来源（大肠杆菌、枯草芽孢杆菌、荧光假单胞菌和谷氨酸棒杆菌）筛选PanD。发现来自谷氨酸棒杆菌的PanD具有最高活性，用该酶进行摇瓶培养时提高了P3HP产量。为进一步提高产量，筛选了宿主菌株并优化了培养条件。在最佳条件下，需氧补料分批发酵中P3HP的产量和含量分别达到10.2 g/L和39.1%（重量/重量[细胞干重]）。迄今为止，这是无VB12情况下最高的P3HP产量。
