A process for production of trehalose by recombinant trehalose synthase and its purification

A comprehensive review on the properties, production, and applications of functional glucobioses

Glucobiose is a range of disaccharides consisting of two glucose molecules, generally including trehalose, kojibiose, sophorose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, and gentiobiose. The difference glycosidic bonds of two glucose molecules result in the diverse molecular structures, physiochemical properties and physiological functions of these glucobioses. Some glucobioses are abundant in nature but have unconspicuous roles on health like maltose, whereas some rare glucobioses display remarkable biological effects. It is unpractical process to extract these rare glucobioses from natural resources, while biological synthesis is a feasible approach. Recently, the production and application of glucobiose have attracted considerable attention. This review provides a comprehensive overview of glucobioses, including their natural sources and physicochemical properties like structure, sweetness, digestive performance, toxicology, and cariogenicity. Specific enzymes used for the production of various glucobioses and fermentation production processes are summarized. Additionally, their versatile functions and broad applications are also introduced.

Production of Trehalose from Maltose by Whole Cells of Permeabilized Recombinant Corynebacterium glutamicum

Trehalose (α-D-glucopyranosyl-1,1-α-D-glucopyranoside) is a stable and nonreducing disaccharide; can be used as sweetener, stabilizer, and humectant; and has many applications in the food, pharmaceutical, and cosmetic industries. Trehalose production from maltose catalyzed by trehalose synthase (TreS) is simple and economically feasible for industrial-scale application. Reducing the cost and enhancing the efficiency of TreS synthesis and the conversion of maltose to trehalose is critical for trehalose production. In this study, the homologous TreS was constitutively overexpressed in Corynebacterium glutamicum ATCC13032 by removing the repressor gene lacIq fragment in the plasmid, and TreS expression could be exempt from the inducer addition and induction process. For cell permeabilization, Triton X-100 was used as a permeabilization agent, and the treatment time was 3 h. In the conversion system, the permeabilized cells of recombinant C. glutamicum were used as biocatalysts, 300 g/L maltose was used as a substrate, and 173.7 g/L trehalose was produced within 12 h under 30 °C and pH 7.0 conditions. In addition, the whole-cell biocatalysts showed promising reusability. This study provides a safe, convenient, practical, and low-cost pathway for the production of trehalose.

Integrated Whole-Cell Biocatalysis for Trehalose Production from Maltose Using Permeabilized Pseudomonas monteilii Cells and Bioremoval of Byproduct

Trehalose is a non-conventional sugar with potent applications in the food, healthcare and biopharma industries. In this study, trehalose was synthesized from maltose using whole-cell Pseudomonas monteilii TBRC 1196 producing trehalose synthase (TreS) as the biocatalyst. The reaction condition was optimized using 1% Triton X-100 permeabilized cells. According to our central composite design (CCD) experiment, the optimal process was achieved at 35°C and pH 8.0 for 24 h, resulting in the maximum trehalose yield of 51.60 g/g after 12 h using an initial cell loading of 94 g/l. Scale-up production in a lab-scale bioreactor led to the final trehalose concentration of 51.91 g/l with a yield of 51.60 g/g and productivity of 4.37 g/l/h together with 8.24 g/l glucose as a byproduct. A one-pot process integrating trehalose production and byproduct bioremoval showed 53.35% trehalose yield from 107.4 g/l after 15 h by permeabilized P. moteilii cells. The residual maltose and glucose were subsequently removed by Saccharomyces cerevisiae TBRC 12153, resulting in trehalose recovery of 99.23% with 24.85 g/l ethanol obtained as a co-product. The present work provides an integrated alternative process for trehalose production from maltose syrup in bio-industry.

Microbial trehalose boosts the ecological fitness of biocontrol agents, the viability of probiotics during long-term storage and plants tolerance to environmental-driven abiotic stress

Despite the impressive gain in agricultural production and greater availability of food, a large portion of the world population is affected by food shortages and nutritional imbalance. This is due to abiotic stresses encountered by plants as a result of environmental-driven perturbations, loss of viability of starter cultures (probiotics) for functional foods during storage as well as the vulnerability of farm produce to postharvest pathogens. The use of compatible solutes (e.g., trehalose, proline, etc.) has been widely supported as a solution to these concerns. Trehalose is one of the widely reported microbial- or plant-derived metabolites that help microorganisms (e.g., biocontrol agents, probiotics and plant growth-promoting bacteria) and plants to tolerate harsh environmental conditions. Due to its recent categorization as generally regarded as safe (GRAS), trehalose is an essential tool for promoting nutrition-sensitive agriculture by replacing the overuse of chemical agents (e.g., pesticides, herbicides). Therefore, the current review evaluated the progress currently made in the application of trehalose in sustainable agriculture. The challenges, opportunities, and future of this biometabolite in food security were highlighted.

Exploitation of carbohydrate processing enzymes in biocatalysis

Exploitation of enzymes in biocatalytic processes provides scope both in the synthesis and degradation of molecules. Enzymes have power not only in their catalytic efficiency, but their chemoselectivity, regioselectivity, and stereoselectivity means the reactions they catalyze are precise and reproducible. Focusing on carbohydrate processing enzymes, this review covers advances in biocatalysis involving carbohydrates over the last 2-3 years. Given the notorious difficulties in the chemical synthesis of carbohydrates, the use of enzymes for synthesis has potential for significant impact in the future. The use of catabolic enzymes in the degradation of biomass, which can be exploited in the production of biofuels to provide a sustainable and greener source of energy, and the synthesis of molecules that have a range of applications including in the pharmaceutical and food industries will be explored.

Trehalose Production Using Recombinant Trehalose Synthase in Bacillus subtilis by Integrating Fermentation and Biocatalysis

Trehalose, a stable nonreducing disaccharide, protects biomolecules against environmental stress. However, trehalose production using secretory trehalose synthase (TreS) by Bacillus subtilis has not been well studied. In this study, a mutant TreS was successfully secreted and expressed in B. subtilis WB800N. The extracellular enzyme activity of TreS regulated by the P₄₃ promoter and SP_PhoD signal peptide in recombinant B. subtilis WB800N reached 23080.6 ± 1119.4 U/L in a 5-L fermenter after optimizing the culture medium, while xpF, skfA, lytC, and sdpC were knocked out. To reduce maltose consumption, malP and amyE corresponding to maltose transporters were further deleted. To simplify the trehalose production process, we invented a fermentation-coupling biocatalysis process involving recombinant bacteria fermentation to secrete TreS and simultaneous conversion of maltose to trehalose by TreS and found that the conversion rate of maltose to trehalose reached 75.5%, suggesting that this is an efficient strategy for large-scale trehalose production using recombinant B. subtilis.

Production of trehalose with trehalose synthase expressed and displayed on the surface of Bacillus subtilis spores

BACKGROUND

Bacillus subtilis spores have been commonly used for the surface display of various food-related or human antigens or enzymes. For successful display, the target protein needs to be fused with an anchor protein. The preferred anchored proteins are the outer-coat proteins of spores; outer-coat proteins G (CotG) and C (CotC) are commonly used. In this study, mutant trehalose synthase (V407M/K490L/R680E TreS) was displayed on the surface of B. subtilis WB800n spores using CotG and CotC individually or in combination as an anchoring protein.

RESULTS

Western blotting, immunofluorescence, dot blot, and enzymatic-activity assays detected TreS on the spore surface. The TreS activity with CotC and CotG together as the anchor protein was greater than the sum of the enzymatic activities with CotC or CotG alone. The TreS displayed on the spore surface with CotC and CotG together as the anchoring protein showed elevated and stable specific activity. To ensure spore stability and prevent spore germination in the trehalose preparation system, two germination-specific lytic genes, sleB and cwlJ, were deleted from the B. subtilis WB800n genome. It was demonstrated that this deletion did not affect the growth and spore formation of B. subtilis WB800n but strongly inhibited germination of the spores during transformation. The conversion rate of trehalose from 300 g/L maltose by B. subtilis strain WB800n(ΔsleB, ΔcwlJ)/cotC-treS-cotG-treS was 74.1% at 12 h (350 U/[g maltose]), and its enzymatic activity was largely retained, with a conversion rate of 73% after four cycles.

CONCLUSIONS

The spore surface display system based on food-grade B. subtilis with CotC and CotG as a combined carrier appears to be a powerful technology for TreS expression, which may be used for the biotransformation of D-maltose into D-trehalose.

Saturation mutagenesis and self-inducible expression of trehalose synthase in Bacillus subtilis

Trehalose is a nonreducing disaccharide synthesized by trehalose synthase (TreS), which catalyzes the reversible interconversion of maltose and trehalose. We aimed to enhance the catalytic conversion of maltose to trehalose by saturation mutagenesis, and constructed a self-inducible TreS expression system by generating a robust Bacillus subtilis recombinant. We found that the conversion yield and enzymatic activity of TreS was enhanced by saturation mutations, especially by the combination of V407M and K490L mutations. At the same time, these saturation mutations were contributing to reducing by-products in the reaction. Compared to WT TreS, the conversion yield of maltose to trehalose was increased by 11.9%, and the k_cat /K_m toward trehalose was 1.33 times higher in the reaction catalyzed by treS^V407M-K490L . treS^V407M-K490L expression was further observed in the recombinant B. subtilis W800N(Δσ^F ) under the influence of P_srfA , P_cry3Aa , and P_srfA-cry3Aa promoters without an inducer. It was shown that P_srfA-cry3Aa was evidently a stronger promoter for treS^V407M-K490L expression, with the intracellular enzymatic activity of recombinant treS^V407M-K490L being over 5,800 U/g at 35 hr in TB medium. These results suggested the combination of two mutations, V407M and K490L, was conducive for the production of trehalose. In addition, the self-inducible TreS^V407M/K490L mutant in the B. subtilis host provides a low-cost choice for the industrial production of endotoxin-free trehalose with high yields.

Improved Expression and Optimization of Trehalose Synthase by Regulation of Pglv in Bacillus subtilis

Trehalose synthase (TreS) converts maltose to trehalose, which has several important functions; therefore, enhancing TreS expression is desirable. Here, a recombinant Bacillus subtilis W800N (ΔamyE)-P_glv strain was constructed to achieve enhanced expression of TreS. Process optimization strategies were developed to improve the expression level of TreS in B. subtilis W800N (ΔamyE)-P_glv. Intracellular activity of TreS was induced using 60 g/L of maltose in shake flask culture. The protein activity reached 5211 ± 134 U/g at 33 °C and pH 7.0 in Luria-Bertani medium. A fed-batch fermentation strategy was applied in a 30 L fermenter containing 18 L terrific broth to achieve high cell density by replacing glycerol with high maltose syrup as a carbon source and an inducer. After 32 h of fermentation, recombinant B. subtilis W800N (ΔamyE)-P_glv activity reached 6850 ± 287 U/g dry cell weight. Our results demonstrate the efficiency of the P_glv promoter in increasing the expression of TreS in B. subtilis W800N (ΔamyE)-P_glv.