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Rice straw is a lignocellulosic biomass, and has been recognized as a renewable organic substance and alternative energy source. In this study, rice straw was pretreated with hypochlorite-hydrogen peroxide (Ox-B) solution. The optimal pretreatment conditions were determined via response surface methodology, and the pretreated rice straw was hydrolyzed with exo-glucanase, endoglucanase, hemicellulase, and β-glucosidase Accellerase 1000™ (endo-glucanase equivalent activity of 1,250 carboxy methyl cellulose (CMC) U/g of rice straw pretreated for 24 h). The optimal conditions were as follows: 60 min pretreatment using Ox-B solution containing 0.6% hypochlorite and 25% hydrogen peroxide for 1 g of rice straw in a total reaction volume of 240 mL. Under these conditions, 406.8 mg of d-glucose and 224.0 mg of d-xylose were obtained from 1 g of rice straw. The fermentation of enzymatic hydrolysates containing 8.14 g/L d-glucose and 4.49 g/L d-xylose with Pichia stipitis generated 3.65 g/L of ethanol with a corresponding yield of 0.37 g/g. The maximum possible ethanol conversion rate is 72.54%.

Hydroquinone galactoside (HQ-Gal) as a potential skin whitening agent was synthesized by the reaction of lactase (beta-galactosidase) from Kluyveromyces lactis, Aspergillus oryzae, Bacillus circulans, and Thermus sp. with lactose as a donor and HQ as an acceptor. Among these lactases, the acceptor reaction involving HQ and lactose with K. lactis lactase showed a higher conversion ratio to HQ-Gal (60.27%). HQ-Gal was purified using butanol partitioning and silica gel column chromatography. The structure of the purified HQ-Gal was determined by nuclear magnetic resonance, and the ionic product was observed at m/z 295 (C12H16O7Na)+ using matrix assisted laser desorption ionization time-of-flight mass spectrometry. HQ-Gal was identified as 4-hydroxyphenyl-beta-d-galactopyranoside. The optimum conditions for HQ-Gal synthesis by K. lactis determined using response surface methodology were 50 mM HQ, 60 mM lactose, and 20 U mL(-1) lactase. These conditions produced a yield of 2.01 g L(-1) HQ-Gal. The half maximal inhibitory concentration (IC50) of diphenylpicrylhydrazyl scavenging activity was 3.31 mM, indicating a similar antioxidant activity compared to beta-arbutin (IC50=3.95 mM). The Ki value of HQ-Gal (0.75 mM) against tyrosinase was smaller than that of beta-arbutin (Ki=1.97 mM), indicating its superiority as an inhibitor. HQ-Gal inhibited (23%) melanin synthesis without being significantly toxic to the cells, while beta-arbutin exhibited only 8% reduction of melanin synthesis in B16 melanoma cells compared with the control. These results indicate that HQ-Gal may be a suitable functional component in the cosmetics industry.

Appreciably elevated levels of dextranase from Arthrobacter oxydans (AODex) isolated from sugar-cane farm soil was resulted from the culture on the Luria-Bertani (LB) medium containing 1%(w/v) soluble starch, glycerol, or dextran. The responsible gene (aodex) was cloned, its nucleotide sequence was determined, and expression of the encoded protein was achieved in Escherichia coli. An open reading frame was composed of 1,863 bp putatively encoding a 68.3 kDa protein. Recombinant A. oxydans dextranase (rAODex) was purified about 16 fold by nickel-nitrilotriacetic acid affinity column chromatography; Km value for dextran T2000 was 0.85 mg/mL (w/v). AODex treatment of stale sugar cane juice resulted in a yield of square and light-colored sugar crystals.

We synthesized a hydroquinone glucoside (HG) as a potential skin-whitening agent using Leuconostoc mesenteroides (B-1299CB BF563) dextransucrase with hydroquinone (HQ) as an acceptor and sucrose as a donor. The product was purified using butanol partitioning and silica gel column chromatography. The structure of the purified HG was determined by nuclear magnetic resonance and the ionic product was observed at m / z 295 (C12, H16, O7 Na) + . HG was identified as 4-hydroxyphenyl-α- d -glucopyranoside. The optimum condition of HG synthesis, determined using a response surface methodology, was 450 mM HQ, 215 mM sucrose, and 0.55 U/mL dextransucrase; the final HG produced was 544 mg/L. The IC 50 of diphenylpicryl-hydrazyl scavenging activity was 3.85 mM indicating a higher antioxidant activity compared to β-arbutin (IC 50 = 6.04 mM). HG-mediated inhibition of lipid peroxidation was 3.51% that of HQ (100%) and much higher than that of β-arbutin (0.81% of HQ). In addition the IC 50 value of nitrite-scavenging activity was 14.76 mM showing a superior scavenging activity to that of β-arbutin (IC 50 = 27.09 mM).

Three epigallocatechin gallate (EGCG) glucosides were synthesized by the acceptor reaction of a glucansucrase from Leuconostoc mesenteroides B-1299CB with EGCG and sucrose. After 1H, 13C, heteronuclear single quantum coherence, 1H–1H correlation spectroscopy, and heteronuclear multiple bond correlation nuclear magnetic resonance analyses, the glucosides were identified as (−)-epigallocatechin gallate 4′′-O-α- d -glucopyranoside (EGCG-G1), (−)-epigallocatechin gallate 7,4′′-di-O-α- d -glucopyranoside (EGCG-G2A), and (−)-epigallocatechin gallate 4′,4′′-di-O-α- d -glucopyranoside (EGCG-G2B). Two of the compounds (EGCG-G1 and EGCG-G2A) are reported for the first time. The EGCG glucosides exhibited antioxidant effects, depending on their structures (EGCG > EGCG-G1 > EGCG-G2A > EGCG-G2B). They also uniformly exhibited greater browning resistance than was observed in EGCG. Also, the water solubility of EGCG-G1, EGCG-G2A, and EGCG-G2B were 69, 126, and 122 times higher, respectively, than that of EGCG.

Background: Production of wheat bran (WB) for human consumption is estimated to be about 90 million tons per year. WB contains abundant source of dietary fiber, minerals, vitamins, and bioactive compounds. WB is a by-product of milling and contains abundant source carbohydrate (60%), protein (12%), fat (0.5%), minerals (2%), and bioactive compounds such as phenolic acids, arabinoxylans, flavonoids, caroteinoids alkylresorcinol and phytosterols. These are known for health promoting properties such as controlling glycemic index, reducing plasma cholesterol level, and reducing the human colon cancer cell growth antioxidant, antimicrobial, anti-inflammatory, and anticarcinogenic activities. Several terpene glycosides such as mogroside V, paenoiflorin, geniposide, rubusoside (Ru), stevioside (Ste), rebaudioside A (RebA), steviol monoside, and stevioside glucoside have been discovered to enhance the solubility of a number of pharmaceutically and medically important compounds that normally show poor solubility in water. Context and purpose of this study: In this study, to increase soluble extraction of polyphenol compounds of WB using Ru, the expression of β-galactosidase from Thermus thermophilus was optimized with different E. coli hosts and with different concentration of lactose inducer instead of isopropyl-1-thio-β-D-galactopyranoside (IPTG) for industrial production. Furthermore, the effect of different steviol glucosides (Ru, Ste, RebA, and SG) on the enhancement of polyphenol compounds extraction from wheat bran was studied. Results: β-galactosidase from Thermus thermophilus was used for the specific conversion of stevioside (Ste) to rubusoside (Ru) with 92% productivity. The enzyme was optimized to be expressed in E. coli. With 7 mM lactose, the β-galactosidase activity expressed was 34.3, 14.2, or 34.4 ± 0.5 U/mL in E. coli BL21(DE3)plysS, Rosetta(DE3)plysS, or BL21(DE3) at 37°C, and 9.8 ± 0.2, 7.0 ± 0.5, or 7.4 ± 0.2 U/mL at 28°C, respectively. The expression of β-galactosidase was dependent on the lactose concentration and the highest activity was obtained with the conditions of 5 mM lactose in E. coli Rosetta(DE3)plysS, 53.3 ± 1.5 U/mL. 78% of the mesophilic proteins was eliminated by heating at 70°C for 15 min with 89% β-galactosidase activity recovery. The total polyphenol content of WB extracted by water, Ru, Ste, rebaudioside A (RebA), and steviol glucosides (SG) were 533.8 ± 9.6 µg/mL, 633.3 ± 1.25 µg/mL, 604.4 ± 10.1 µg/mL, 654.8 ± 26.5 µg/mL, and 601.2 ± 33.4 µg/mL, respectively. The DPPH radical scavenging activity prepared by water, Ru, Ste, RebA, and SG extraction were 8.76 ± 0.3 mg/mL, 4.87 ± 0.3 mg/mL, 5.34 ± 0.22 mg/mL, 7.27 ± 0.1 mg/mL, and 7.82 ± 0.02 mg/mL, respectively. Conclusions: To increase soluble extraction of polyphenol compounds of WB using Ru, the expression of β-galactosidase from Thermus thermophilus was optimized with different E. coli hosts and with different concentration of lactose inducer instead of isopropyl-1-thio-β-D-galactopyranoside (IPTG) for industrial production of the enzyme. The highest antioxidant activity was shown in WB extracted by Ru. The number of glucosyl units attached to steviol can possibly affect the efficiency of antioxidant activity of WB extracted by steviol glucosides. Keywords: Rubusoside, s-galactosidase, lactose induction, immobilized enzyme, wheat bran, steviol glucosides