Immobilization of the recombinant (His) 6 -tagged l -arabinose isomerase from Thermotoga maritima on epoxy and cupper-chelate epoxy supports

Production of D -tagatose, bioethanol, and microbial protein from the dairy industry by-product whey powder using an integrated bioprocess

We designed and constructed a green and sustainable bioprocess to efficiently coproduce D -tagatose, bioethanol, and microbial protein from whey powder. First, a one-pot biosynthesis process involving lactose hydrolysis and D -galactose redox reactions for D -tagatose production was established in vitro via a three-enzyme cascade. Second, a nicotinamide adenine dinucleotide phosphate-dependent galactitol dehydrogenase mutant, D36A/I37R, based on the nicotinamide adenine dinucleotide-dependent polyol dehydrogenase from Paracoccus denitrificans was created through rational design and screening. Moreover, an NADPH recycling module was created in the oxidoreductive pathway, and the tagatose yield increased by 3.35-fold compared with that achieved through the pathway without the cofactor cycle. The reaction process was accelerated using an enzyme assembly with a glycine-serine linker, and the tagatose production rate was 9.28-fold higher than the initial yield. Finally, Saccharomyces cerevisiae was introduced into the reaction solution, and 266.5 g of D -tagatose, 162.6 g of bioethanol, and 215.4 g of dry yeast (including 38% protein) were obtained from 1 kg of whey powder (including 810 g lactose). This study provides a promising sustainable process for functional food (D -tagatose) production. Moreover, this process fully utilized whey powder, demonstrating good atom economy.

Study on the synthesis of pine sterol esters in solvent-free systems catalyzed by Candida rugosa lipase immobilized on hydrophobic macroporous resin

BACKGROUND

Pine sterol ester is a type of novel food source nutrient with great advantages in lowering blood cholesterol levels, inhibiting tumors, preventing prostate enlargement, and regulating immunity. Macroporous resins with large specific surface area, stable structures, and various functional groups (epoxy, amino, and octadecyl groups) have been selected for immobilization of Candida rugosa lipase (CRL) to improve its stability and efficiency in the synthesis of pine sterol esters. A solvent-free strategy using oleic acid (substrate) as an esterification reaction medium is an important alternative for avoiding the use of organic solvents.

RESULTS

The immobilization conditions of CRL immobilized on several types of commercial macroporous resins were optimized. Fortunately, by adsorption (hydrophobic interaction), a high immobilization efficiency of CRL was obtained using macroporous resins with hydrophobic octadecyl groups with an immobilization efficiency of 86.5%, enzyme loading of 138.5 mg g-1 and enzyme activity of 34.7 U g-1 . The results showed that a 95.1% yield could be obtained with a molar ratio of oleic acid to pine sterol of 5:1, an enzyme amount of 6.0 U g-1 (relative to pine sterol mass) at 50 °C for 48 h.

CONCLUSION

The hydrophobic macroporous resin (ECR8806M) with a large specific surface area and abundant functional groups was used to achieve efficient immobilization of CRL. CRL@ECR8806M is an efficient catalyst for the synthesis of phytosterol esters and has the potential for further large-scale applications. Therefore, this simple, green, and low-cost strategy for lipase immobilization provides new possibilities for the high-efficiency production of pine sterol esters and other food source nutrients. © 2023 Society of Chemical Industry.

Galactose to tagatose isomerization at moderate temperatures with high conversion and productivity

There are many industrially-relevant enzymes that while active, are severely limited by thermodynamic, kinetic, or stability issues (isomerases, lyases, transglycosidases). In this work, we study Lactobacillus sakeil-arabinose isomerase (LsLAI) for d-galactose to d-tagatose isomerization—that is limited by all three reaction parameters. The enzyme demonstrates low catalytic efficiency, low thermostability at temperatures > 40 °C, and equilibrium conversion < 50%. After exploring several strategies to overcome these limitations, we show that encapsulating LsLAI in gram-positive Lactobacillus plantarum that is chemically permeabilized enables reactions at high rates, high conversions, and elevated temperatures. In a batch process, this system enables ~ 50% conversion in 4 h starting with 300 mM galactose (an average productivity of 37 mM h⁻¹), and 85% conversion in 48 h. We suggest that such an approach may be invaluable for other enzymatic processes that are similarly kinetically-, thermodynamically-, and/or stability-limited.

Production of tagatose, a sugar substitute, by isomerization of galactose suffers from unfavorable enzymatic kinetics, low enzyme stability, and low equilibrium constant. Here, the authors simultaneously overcome these limitations by encapsulating l-arabinose isomerase in permeabilized Lactobacillus plantarum.