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.
The utilization of biomass in the production of renewable bioenergy and biomaterials
has been a popular topic since the past decades as they are rich in carbohydrates.
Most biomasses, such as wood, monocotyledons, and agriculture residues, need to be pretreated
before the conversion of carbohydrates in order to break down the recalcitrant cell
wall structure and increase the fiber accessibility. To date, a variety of pretreatment methods
have been developed that vary from physical to chemical and biological methods. Pretreatment
processes affect the cell wall physical structure as well as the chemical structure
of the cell wall constituents. Comparing to the studies of the cellulose and hemicelluloses
structural changes during pretreatment, such studies on lignin are relatively limited. On
the other hand, in order to utilize the part of lignin from biorefinery processes,
the understanding of the lignin structural changes during the refining process becomes important. In this study,
typical pretreatment methods such as hydrothermal pretreatment, alkaline pretreatment, biodegradation, and
oxidative pretreatment are introduced and their corresponding impacts on the lignin structures are reviewed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.