Enzymatic synthesis of 3-hydroxypropionic acid at high productivity by using free or immobilized cells of recombinant Escherichia coli

Abstract

3-Hydroxypropionic acid (3-HP) is an important platform chemical for organic synthesis and high performance polymers. Despite a wealth of reports related to 3-HP biosynthesis in microorganisms, its industrial application still requires further research because of low titer and productivity. Herein an effective enzymatic method for the synthesis of 3-HP was achieved by using free or immobilized recombinant Escherichia coli BL21(DE3) cells harboring a nitrilase gene from environmental sample (NIT190). Under the optimal conditions (100mmol/L Tris-HCl buffer, pH 8.0, 30°C), the maximum substrate concentration which could be completely hydrolyzed by using free cells within 24h was 4.5mol/L (319.5g/L). Furthermore, immobilization of the whole cells enhanced their substrate tolerance (up to 7.0mol/L), stability, and reusability. The immobilized cells could be reused for up to 30 batches, and 70% of enzyme activity was retained after 74 batches in distilled water. The titer (184.7g/L) and productivity (36.9g/(Lh)) were obtained by isolation and purification of 3-HP from the first 30 batches. These results demonstrate that the immobilized cells have potential industrial application for the synthesis of 3-HP.