Cheng-Chun Chou

Enhancement of antioxidant activity, total phenolic and flavonoid content of black soybeans by solid state fermentation with Bacillus subtilis BCRC 14715

In the present study, a solid state fermentation of black soybeans with Bacillus subtilis BCRC 14715 was performed. The effect of fermentation on the changes of total phenolic and flavonoid content and antioxidant activities including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging effect, and Fe(2+)-chelating ability exerted by various solvent (water, 80% methanol, 80% ethanol, 80% acetone) extracts of black soybeans was examined. It was found that fermentation enhanced the total phenolic and flavonoid content as well as antioxidant activity of the black soybean extract. Among the various extracts examined, the acetone extract of fermented black soybeans showed the highest total phenolic and flavonoid content. The acetone extract and the methanol extract of fermented black soybeans showed the highest DPPH free radical-scavenging effect and Fe(2+)-chelating ability, respectively. Analysis of extraction yields showed that the active principle associated with the DPPH radical-scavenging effect was most efficiently extracted from black soybeans using water, regardless of fermentation. Water and methanol effectively extract the Fe(2+)-chelating principles from non-fermented and fermented black soybeans, respectively.

Antibacterial activity of N-alkylated disaccharide chitosan derivatives

Antibacterial activity of the water-soluble N-alkylated disaccharide chitosan derivatives against Escherichia coli and Staphylococcus aureus was investigated. It was found that the antibacterial activity of chitosan derivatives was affected by the degree of substitution (DS) with disaccharide and the kind of disaccharide present in the molecule. Regardless the kind of disaccharide linked to the chitosan molecule, a DS of 30-40%, in general, exhibited the most pronounced antibacterial activity against both test organisms. E. coli and S. aureus were most susceptible to cellobiose chitosan derivative DS 30-40% and maltose chitosan derivative DS 30-40%, respectively, among the various chitosan derivatives examined. Although the disaccharide chitosan derivatives showed less antibacterial activity than the native chitosan at pH 6.0, the derivatives exhibited a higher activity than native chitosan at pH 7.0. Antibacterial activity of the chitosan derivatives (DS 30-40%) against E. coli increased as the pH increased from 5.0 and reached a maximum around the pH of 7.0-7.5. The effect of pH on the antibacterial activity of chitosan derivatives against S. aureus was not as pronounced as that observed with E. coli. Population reduction of E. coli or S. aureus in nutrient broth increased markedly upon increasing the concentration of chitosan derivatives from 0 to 500 ppm. No marked increase in population reduction was noted with further increase in the concentration of chitosan derivatives even up to 2000 ppm.

Enzymatic Production of Galactooligosaccharides by β-Galactosidase from Bifidobacterium longum BCRC 15708

The production of galactooligosaccharides (GOSs) by transgalactosylation using beta-galactosidase from Bifidobacterium longum BCRC 15708 was studied. Other than lactose, galactose, and glucose, two types of GOSs, tri- and tetrasaccharides, were formed after beta-galactosidase action on 40% lactose. Trisaccharides were the major type of GOS formed. Generally, an increase of the initial lactose concentration in the reaction mixture resulted in a higher GOS production. A maximum yield of 32.5% (w/w) GOSs could be achieved from 40% lactose solution at 45 degrees C, pH 6.8, when the lactose conversion was 59.4%. The corresponding productivity of GOSs was 13.0 g/(L.h). Transgalactosylation activity of beta-galactosidase from a test organism showed a relatively lower sensitivity toward glucose and galactose than that from other organisms. The addition of 5% or 10% glucose or galactose to the reaction mixture did not significantly (p>0.05) reduce the transgalactosylation reaction of beta-galactosidase.

Soyfoods and soybean products: from traditional use to modern applications

Soybean products (soyfoods), reported as potential functional foods, are implicated in several health-enhancing properties, such as easing the symptoms of postmenopausal women, reducing the risk of osteoporosis, preventing cardiovascular disease, and antimutagenic effects. Isoflavone, for example, is one of the most important compounds abundantly found in soybean, mainly accounting for the health-enhancing properties as mentioned earlier. However, most biological activities of isoflavones are mainly attributed to their aglycone forms. It has also been demonstrated that isoflavone aglycones are absorbed faster and in greater amount than their glycosides in human intestines. Fortunately, deglycosylation of isoflavones can be achieved during fermentation process by several strains such as lactic acid bacteria, basidiomycetes, filamentous fungus, and Bacillus subtilis with their β-glucosidase activity. This article presents an overview of soybean’s chemistry, application, state-of-the-art advances in soybean fermentation processing and products as well as their applications in food and pharmaceutical industries. Different compounds, such as isoflavone, dietary fibers, and proteins which exhibit significant bioactivities, are summarized. The roles of different microorganisms in bioconversion and enhancement of bioactivities of fermented soybean are also discussed.

Preparation, water solubility and rheological property of the N-alkylated mono or disaccharide chitosan derivatives

N-alkylation of chitosan was performed in a mixture of methanol and 1% acetic acid containing different amounts of monosaccharides or disaccharides including glucose, galactose, glucosamine, fructose, lactose, maltose and cellobiose. All the N-alkylated chitosan derivatives with monosaccharides were insoluble in aqueous solution (pH 7), while N-alkylated chitosan derivatives with disaccharides were easily soluble in distilled water, and the N-alkylated chitosan derivatives with lactose were soluble only at high pH. The degree of substitution (DS) of the N-alkylated chitosan derivatives increased with increasing disaccharides levels and with increasing reaction time. The reduced viscosity of the N-alkylated chitosan derivatives with disaccharides decreased with increasing DS. Apparent viscosity and pseudoplasticity of the N-alkylated disaccharide containing derivative solutions generally decreased with increasing DS. Although apparent viscosities of N-alkylated chitosan derivatives with low DS decreased with increase in pH or ionic strength, changes in high DS N-alkylated chitosan derivatives with pH values or ionic strength were not marked.

Enrichment of two isoflavone aglycones in black soymilk by using spent coffee grounds as an immobiliser for β-glucosidase.

Spent coffee grounds, discarded as environmental pollutants, were adopted as enzyme immobilisation solid carriers instead of commercialised solid supports to establish an economical catalytic system. β-Glucosidase was covalently immobilised onto spent coffee grounds for the conversion of isoflavone glycosides into their aglycones in black soymilk. Optimum conditions were determined to be 40°C and pH 6 using 4-nitrophenyl β-D-glucuronide as an indicator. Operational reusability was confirmed for more than 30 batch reactions and the storage stability was capable of sustaining its highest catalytic activity for 20 days. The kinetic parameters including rate constant (K), time (τ(50)) in which 50% of isoflavone deglycosylation was reached, and time (τ(complete)) required to achieve complete isoflavone deglycosylation, were 0.16±0.02 min(-1), 4.54±0.32 min, 60 min for daidzin and 0.16±0.02 min(-1), 2.28±0.11 min, 60 min for genistin, respectively. The total aglycone content in black soymilk was enriched by 67.14±0.60% in the enzymatic treatment of 60 min duration.

Volatile components of the enzyme-ripened sufu, a Chinese traditional fermented product of soy bean

In the present study, sufu, a soft cheese-like oriental fermented food, was prepared by ripening the salted-tofu cubes in Aspergillus oryzae-fermented soybean-rice koji at 37°C for 16 days (16-day sufu). Sufu was further held at room temperature for another 30 days (46-day sufu). The volatile components of the non-fermented tofu cubes and the sufu products were identified and quantified by GC and GC-MS. A total of 70 volatile compounds including 20 aldehydes, 18 alcohols, 16 esters, 5 ketones, 5 acids and 6 other compounds were identified. Sufu products contained more volatile compounds than non-fermented tofu cubes qualitatively and quantitatively. After 16-days of ripening, fatty acid, aldehyde and ester were noted to be the dominant volatile fractions. In contrast, the 46-day sufu contained ester, and alcohol as the major volatile fractions. They comprise approximately 63.9% of the total volatile components.

The effect of temperature and length of heat shock treatment on the thermal tolerance and cell leakage of Cronobacter sakazakii BCRC 13988.

Enterobacter sakazakii is an emerging opportunistic pathogen associated with life-threatening illnesses in infants, with infant formula serving as the principal mode of transmission. In the present study, C. sakazakii (formely E. sakazakii) BCRC 13988 was subjected to various heat shock treatments (42-48 degrees C for 5-15 min). Its subsequent survival at 51 degrees C and the leakage of intracellular materials was investigated. It was found that 47 degrees C was the maximum growth temperature of the test organism. In addition, heat shock enhanced the thermal tolerance of C. sakazakii BCRC 13988. Within heat shock temperatures between 42 and 47 degrees C, the thermal tolerance enhancing effect increased as the length or temperature of the heat shock treatment was increased. However, increasing the heat shock temperature to 48 degrees C reduced the thermal tolerance enhancing effect. Among the various heat shocked cells examined, the 47 degrees C-15 min-heat shocked C. sakazakii exhibited the highest thermal tolerance. Moreover, electron micrograph analysis showed that heat shock treatment caused damage and disruption in C. sakazakii cells. There was a significant increase (P<0.05) in the leakage of nucleic acid and protein in the supernatant of the heat shocked cell suspension that increased as the temperature and duration of heat shock increased.

Fermentation temperature affects the antioxidant activity of the enzyme-ripened sufu, an oriental traditional fermented product of soybean.

In this study, sufu, a Chinese traditional fermented product of soybean, was prepared by ripening salted tofu cubes in the mash of Aspergillus oryzae-fermented rice-soybean koji possessing various hydrolytic enzymes at 25°C, 37°C and 45°C. Antioxidant activity including 2,2-diphenyl-2-picylhydoxyl (DPPH) radical-scavenging activity, Fe(2+)-chelating ability and reducing power exerted by the methanol extract of sufu was determined and compared with that of the non-fermented tofu extract. It was found that antioxidant activity of the sufu extracts was, generally, higher than the non-fermented tofu extract. Ripening temperature and the duration of ripening period affected the antioxidant activity of the sufu extracts. Taking into account of extraction yields, the sufu product ripened at 45°C for 16 days showed the most profound enhancement in the DPPH radical-scavenging effect and Fe(2+)-iron-chelating ability, which is 3.4 and 11.5 folds, respectively, that noted with the non-fermented tofu.

Fermentation with Bacillus spp. as a bioprocess to enhance anthocyanin content, the angiotensin converting enzyme inhibitory effect, and the reducing activity of black soybeans

Food possessing anthocyanins, angiotensin converting enzyme (ACE) inhibitory activity or reducing activity show beneficial effect on human health. To develop healthy food, black soybeans were fermented with either Bacillus subtilis BCRC 14715 or Bacillus sp. CN11, or a mixture of both Bacillus spp. in the present study. The anthocyanin content, the ACE inhibitory activity and the reducing power of the fermented black soybean were then examined. It was found that the ACE inhibitory activity of the extracts of bean and viscous material from the fermented black soybeans varied with extraction solvents and starter organism, yet increased as the fermentation period was extended, regardless of starter organism. After 18 h of fermentation, the water extract of bean showed less ACE inhibitory activity than did the respective 80% ethanol extract. While the water extract of viscous material showed a higher ACE inhibitory activity than the respective ethanol extract. With respect to extraction yield, it was found that the ACE inhibitor in the fermented black soybean could be extracted more efficiently with water than 80% ethanol. Fermentation with B. subtilis BCRC 14715 was also found to increase the anthocyanin content of black soybean and the reducing activity of the extracts. Finally, the 80% ethanol extract showed a higher reducing activity than the water extract.