Resolution and synthesis of optically active alcohols with immobilized water-soluble proteins from green pea, soybean and buckwheat as new bio-catalysts

Buckwheat proteins: functionality, safety, bioactivity, and prospects as alternative plant-based proteins in the food industry

The need for protein in human nutrition is rapidly increasing because of the increasing world population and consumer preference for high-protein foods. Plant proteins are gaining attention as sustainable means of meeting the global protein need due to their lower carbon footprint. Nonetheless, the food industry has neglected or underutilized many plant proteins, including buckwheat protein. Buckwheat is a pseudocereal and its groats contain beneficial components such as proteins, dietary fiber, vitamins, and bioactive polyphenols. The protein quality of buckwheat seeds varies between the tartary and common buckwheat types; both are gluten-free and contain considerable amount of indispensable amino acids. This review provides a detailed discussion on the profile, amino acid composition, digestibility, allergenicity, functional properties, and bioactivity of buckwheat proteins. Prospects of processing buckwheat for improving protein digestibility and deactivating allergenic epitopes were also discussed. Based on the literature, buckwheat protein has a tremendous potential for utilization in structuring food products and developing peptide-based functional foods for disease prevention. Future research should develop new processing technologies for further improvement of the quality and functional properties of buckwheat protein in order to facilitate its utilization as an alternative plant-based protein toward meeting the global protein supply.

An HASApf-redoxin complex causing asymmetric catalytic oxidation via the regenerative formation of a reactive oxygen species

A PP (pea)-HASApf-redoxin complex eluted from encapsulated PP gel with aeration displays asymmetric oxidation activity over 200 times greater than that of a similar protein expressed by E. coli cells. The intermediate spin, identified in the ESR spectrum, appears at g = 4.3 and g = 2.0, suggesting that an iron electron-transfer system for the asymmetric oxidation of secondary alcohols may be successfully created by the PP-HASApf-redoxin complex (39 kDa). FTIR experiments provided values νs(SO2) ≈ 950-1050 cm(-1) and νas(SO2) ≈ 1100-1200 cm(-1) for metal-bound sulfinate S-O and Fe-O vibrations. The sulfur and iron detected by physicochemical inspection (IC/ICP-AES) may facilitate the electron transport of a sulfate-iron complex (e.g., rubredoxin (6 kDa) or ferredoxin (9 kDa)) to the HASApf (21 kDa). The observations are consistently acceptable; i.e., the oxygen-driven PP-HASApf-redoxin complex functions regenerate via the successive asymmetric catalytic event - Fe(ii) + O2 → Fe(iii)-O-O(-) → Fe(iv) = O (oxidizing rac- or rac-) → Fe(ii) + H2O. Therefore, the use of a raw biomaterial as a PP-HASApf-redoxin complex-catalytic system for asymmetric oxidation is an important novelty, despite the apparent difficulties in working with pure dehydrogenase enzymatic/redox-cofactor systems for biotransformation.

Cross-linked protein complex exhibiting asymmetric oxidation activities in the absence of added cofactor

A protein complex (PC) suspension exhibits asymmetric biooxidation activities in the absence of any added cofactor such as NAD(P)(+) or FAD. It can be extracted from pea protein (PP)-gel (PP encapsulated with Ca(2+) alginate gel and aerated in air for several hours) using hot water by rotary shaking and powdered by the following three steps: (1) forming precipitates from the suspension using 30% (w/v) aqueous (NH(4) )(2) SO(4) , (2) crosslinking the precipitates with 0.25% (v/v) GA, and (3) preparing the cross-linked powder by freeze-drying. The cross-linked PC (CLPC) performed asymmetric oxidation of the toward (R)-isomers of rac-1 and rac-2 in 50 mM glycine-NaOH (pH 9.0) buffer/DMSO cosolvent [2.07% (v/v)] with high enantioselectivity; thus, the (S)-isomers can be obtained in greater than 99% ee from the corresponding rac-p-substituted naphthyl methyl carbinol (rac-1 and rac-2). The CLPC activity was not only competitively inhibited by addition of either 1.0 mM ZnCl(2) or a chelating agent such as 1.0 mM EDTA but also denatured by pretreatments: autoclaving at 121°C (20 min) or using 6.0 M guanidine-HCl containing 50 mM DTT. These results indicated that the PC catalytic process may utilize an electron transfer system incorporating a redox cation (e.g., Fe(2+) ⇄ Fe(3+) or Zn). Therefore, the newly introduced CLPC can asymmetrically oxidize the substrates without the addition of any cofactor resulting in a low-cost organic method. Overall, our results show that the CLPC is an easily prepared, low-cost reagent that can function under mild conditions and afford stereoselectivity, regioselectivity, and substrate specificity.

Treatment of germinated wheat to increase levels of GABA and IP6 catalyzed by endogenous enzymes

We found that the levels of bioactive products from wheat can be increased dramatically by manipulating germination conditions and taking advantage of the activity of endogenous enzymes. The yield of phytic acid (IP(6)) from wheat germinated in the presence of high, controlled levels of dissolved oxygen (188 +/- 28 mg/100 g wheat) was almost three times greater than that from wheat germinated with no supplemental oxygen (74 +/- 10 mg/100 g wheat). The yield of gamma-aminobutyric acid (GABA) from wheat germinated in the presence of uncontrolled levels of dissolved oxygen was 18 +/- 3 times greater than that from nonsupplemented wheat (1 mg/100 g wheat). The concentration of GABA was much greater in wheat germ than in whole wheat, and the yield of GABA from wheat germ processed with supplemental water (163 +/- 7 mg/100 g wheat germ) was notably greater than that from wheat germ processed with no supplemental water (100 +/- 2 mg/100 g wheat germ). In contrast, IP(6) was more concentrated in wheat bran, and the yield of IP(6) from wheat bran processed with supplemental water (3100 +/- 12 mg/100 g wheat bran) was notably higher than that from wheat bran processed with no supplemental water (2420 +/- 13 mg/100 g wheat bran). We conclude that the large amount of GABA extracted from wheat germ is likely due to high glutamate decarboxylase activity and low aminotransferase activity and that the large amount of IP(6) extracted from wheat bran is likely due to high levels of tyrosinase activity. Our findings indicate that bioactive molecules such as GABA and IP(6) can be successfully mass-produced by taking advantage of endogenous enzymatic activities.

Ability of different biomaterials to enantioselectively catalyze oxidation and reduction reactions

We studied the ability of different biomaterials to enantioselectively catalyze oxidation or reduction reactions with the help of substrate rac-1-m or p-ArCH(OH)Me and the 1-o-ArC(O)Me derivatives. Apoenzyme (NAD(P)(+)-dependent secondary alcohol dehydrogenase(NAD(P)-E)) and cofactor (NAD(P)(+)) were activated by preincubating immobilized aqueous plant leaf (e.g., young wheat leaves), cereal tissue (wheat bran), vegetable (e.g., carrot), and seaweed (e.g., wakame seaweed) solutions, and the NAD(P)-E oxidized only (R)-isomers highly enantioselectively. Thus, greater than 99% ee(s) of (S)-isomers (1m-5m and 1p-5p) can be obtained from corresponding rac-1-m or p-ArCH(OH)Me. Further, immobilized chlorella cells and immobilized baker's yeast can reduce highly stereoselectively; greater than 99% ee(s) of (S)-isomers (1o-5o) can be obtained from corresponding 1-o-ArC(O)Me. Specific use of each isomer ((S)-6 and (R)-6) with greater than 99% ee(s) of racemic-1-2-NpCH(OH)Me becomes possible through selective use of NAD(P)-E eluted from artemisia vulgaris indica leaves and young wheat leaves. We suggest that the pH of the reaction media can determine not only the direction of NAD(P)-E, toward enantioselectively catalyzed oxidation (pH > 7.0) or reduction reaction (pH < 7.0), but also the regioselective reactivity of NAD(P)-E to the substrate o- (pH < 7.0), m-, and p-substituted groups (pH > 7.0). Thus, in comparison to current biocatalysts, several biomaterials can serve as asymmetric reagent bases, providing easily obtained, low-cost natural catalysts with stereoselectivity, regioselectivity, and substrate specificity that work under mild conditions for asymmetric synthesis of organic compounds.

Chiral resolution function with immobilized food proteins

We confirmed that an NAD(P)+-dependent secondary alcohol dehydrogenase (NAD(P)-E) can be easily and effectively isolated from pea, soybean, and wheat proteins immobilized with calcium alginate gel (IPP, ISP, and IWP, respectively). The estimated molecular mass of NAD(P)-E is 138.7 kDa, and the concentrations of NAD(P)-E in solution are 36.2 (IPP), 53.9 (ISP), and 93.7 (IWP) microg/mL. The NAD(P)-E oxidizes only (R)-isomers highly enantioselectively; thus, greater than 99% ee(s) of (S)-isomers can be obtained from corresponding rac-aryl methyl carbinols (1, 2a-6a, and 2b-7b). The amount of food protein needed for 1 g of substrate (B/S ratio) is approximately 20. Thus, in comparison to current biocatalysts, certain food proteins can serve as asymmetric reagent bases, providing easily obtained, low-cost natural catalysts with stereoselectivity, regioselectivity, and substrate specificity that work under mild conditions for asymmetric synthesis of organic compounds. Moreover, this "fourth" function of food may help build a sustainable society by synthesizing optically active secondary alcohols in an environmentally friendly manner.

Resolution and synthesis of optically active alcohols with immobilized ovalbumin and pea protein as new bio-catalysts

It was found that ovalbumin stereoselectively oxidized one of the enantiomers of p-substituted racemic alcohols, thereby providing optically active alcohols with high optical purities. It was found out that, when used appropriately in combination with immobilized pea protein, immobilized ovalbumin made it possible to resolve and synthesize racemic 1-(2-naphthyl)ethanol, 1-phenylethanol, and 1-phenyl-1-propanol. Immobilized ovalbumin could be continuously recycled at least three times without lowering the yield and purity of the products. These results suggested that cereals, beans, and ovalbumin might have additional fourth function among conventional foods. Namely, there might contain nutritional, sensory, biologically regulatory and bio-catalytic functions in conventional foods.