Optimization of whole-cell biotransformation for scale-up production of α-arbutin from hydroquinone by the use of recombinant Escherichia coli

Abstract

α-Arbutin is an effective skin-whitening cosmetic ingredient and hyperpigmentation therapy agent. It can be synthesized by one-step enzymatic glycosylation of hydroquinone (HQ), but limited by the low yield. Amylosucrase (Amy-1) from Xanthomonas campestris pv. campestris 8004 was recently identified with high HQ glycosylation activity. In this study, whole-cell transformation by Amy-1 was optimized and process scale-up was evaluated in 5000-L reactor. In comparison with purified Amy-1, whole-cell catalyst of recombinant E. coli displays better tolerance against inhibitors (oxidized products of HQ) and requires lower molar ratio of sucrose and HQ to reach high conversion rate (> 99%). Excess accumulation of glucose (0.6–1.0 M) derived from sucrose hydrolysis inhibits HQ glycosylation rate by 46–60%, which suggests the importance of balancing HQ glycosylation rate and sucrose hydrolysis rate by adjusting the activity of whole-cell catalyst and HQ-fed rate. Using optimal conditions, 540 mM of final concentration and 95% of molar conversion rate were obtained within 13–18 h in laboratory scale. For industrial scale-up production, 398 mM and 375 mM of final concentration with high conversion rates (~ 95%) were obtained in 3500-L and 4000-L of reaction volume, respectively. These yields and productivities (4.5–4.9 kg kL −1 h −1 ) were the highest by comparing to the best we known. Hence, high-yield production of α-arbutin by batch-feeding whole-cell biotransformation was successfully achieved in the 5000-L reaction scale.

Production of α-arbutin from Hydroquinone by Bacillus subtilis TISTR 1248 and Xanthomonas campestris TISTR 2065

“…The batch-feeding whole-cell biocatalysis by amylosucrase was designed to eliminate hydroquinone inhibition, resulting enhanced yield (306 mM) and molar conversion rate (95%) (Zhu et al, 2019a). Process scale-up of these system was evaluated in 5000-L reactor, producing the highest yields (398 mM per 4000-l reaction volume) and productivities (4.5-4.9 kg kl −1 h −1 ) which can be successfully applied for industrial production of α-arbutin (Zhu et al, 2019b). For our further investigations, a fed-batch strategy and engineered E. coli containing enzyme might be determined to enhance arbutin production.…”

Architecture, Function, Regulation, and Evolution of α-Glucans Metabolic Enzymes in Prokaryotes

“…Over the past years, amylosucrases have attracted more attention due to their capability of isomerization and transglycosylation. To date, many efforts are pursued to engineer amylosucrase enzyme with better thermal stability properties, , higher yield of sweeteners production through isomerization (turanose: glucose α(1→3)-fructose), trehalulose (glucose α(1→1)-fructose), and to improve their ability to glycosylate unnatural acceptors …”

Recent Progress on Feasible Strategies for Arbutin Production

“…8004 (Amy-1) generated 306 mM of α-arbutin in 15 h with a 95% conversion rate of HQ ( Zhu et al, 2019a ). This production process was scaled-up in a 5000 L reactor and achieved 108 g/L of α-arbutin with a 95% molar conversion rate ( Zhu et al, 2019b ).…”