Efficient Allitol Bioproduction from D-Fructose Catalyzed by Recombinant E. coli Whole Cells, and the Condition Optimization, Product Purification

Light Controlled Nanobiohybrids for Modulating Chiral Alcohol Synthesis

The modulation of whole-cell activity presents a considerable challenge in biocatalysis. Conventional approaches to whole-cell catalysis, while having their strengths, often rely on complex and deliberate enzyme designs, which could result in difficulties in activity modulation and prolonged response times. Additionally, the activity of intracellular enzymes in whole-cell catalysis is influenced by temperature. To address these limitations, we introduced a relationally designed nanobiohybrid system that utilized light to modulate whole-cell catalysis for chiral alcohol production. By incorporating platinum nanoparticles onto Rhodotorula sp. cell surfaces, the nanobiohybrid capitalized on the photothermal properties of the nanoparticles to regulate the overall cell activity. When exposed to light, the Pt nanoparticles generate heat through the photothermal effect, consequently leading to an increase in the catalytic activity of the whole cells. This innovative approach facilitates control over whole-cell production and provides an efficient method for regulating biocatalytic processes. The findings of this study demonstrate the significant potential of switchable control strategies in biomanufacturing across a wide range of industries.

D-Allulose (D-Psicose) Biotransformation From Allitol by a Newly Found NAD(P)-Dependent Alcohol Dehydrogenase From Gluconobacter frateurii NBRC 3264 and the Enzyme Characterization

The NAD(P)-dependent alcohol dehydrogenase (ADH) gene was cloned from Gluconobacter frateurii NBRC 3264 and expressed in Escherichia coli BL21 star (DE3). The expressed enzyme was purified and the characteristics were investigated. The results showed that this ADH can convert allitol into D-allulose (D-psicose), which is the first reported enzyme with this catalytic ability. The optimum temperature and pH of this enzyme were 50°C and pH 7.0, respectively, and the enzyme showed a maximal activity in the presence of Co²⁺. At 1 mM Co²⁺ and allitol concentrations of 50, 150, and 250 mM, the D-allulose yields of 97, 56, and 38%, respectively, were obtained after reaction for 4 h under optimal conditions, which were much higher than that obtained by using the epimerase method of about 30%.

Reconstruction of a Cofactor Self-Sufficient Whole-Cell Biocatalyst System for Efficient Biosynthesis of Allitol from d-Glucose

The combined catalysis of glucose isomerase (GI), d-psicose 3-epimerase (DPEase), ribitol dehydrogenase (RDH), and formate dehydrogenase (FDH) provides a convenient route for the biosynthesis of allitol from d-glucose; however, the low catalytic efficiency restricts its industrial applications. Here, the supplementation of 0.32 g/L NAD⁺ significantly promoted the cell catalytic activity by 1.18-fold, suggesting that the insufficient intracellular NAD(H) content was a limiting factor in allitol production. Glucose dehydrogenase (GDH) with 18.13-fold higher activity than FDH was used for reconstructing a cofactor self-sufficient system, which was combined with the overexpression of the rate-limiting genes involved in NAD⁺ salvage metabolic flow to expand the available intracellular NAD(H) pool. Then, the multienzyme self-assembly system with SpyTag and SpyCatcher effectively channeled intermediates, leading to an 81.1% increase in allitol titer to 15.03 g/L from 25 g/L d-glucose. This study provided a facilitated strategy for large-scale and efficient biosynthesis of allitol from a low-cost substrate.