Fish skin, a by-product from fish processing industries, still contains a significant amount of protein-rich material. Gelatin was extracted from Nile tilapia skin with the yield 20.77±0.80 % wet weight. Gelatin was then separately hydrolyzed by proteases, including bromelain, papain, trypsin, flavourzyme, alcalase and neutrase. Low molecular weight gelatin hydrolysate (<10 kDa) has a great potential as an antioxidant agent. Flavourzyme hydrolysate has potent activity on ABTS radical scavenging (1,413.61±88.74 μg trolox/ mg protein) and also inhibits the oxidation of linoleic acid at a high level (59.74±16.57 % inhibition). The greatest reducing power is in alcalase hydrolysate (4.951±1.577 mM trolox/mg protein). While, bromelain hydrolysate has the highest ferrous ion chelating activity (86.895±0.061 %). Evaluation of the angiotensin-I-converting enzyme's inhibitory activity indicates that all hydrolysates have great potency as an antihypertensive agent. All studied tilapia skin gelatin hydrolysates contain potent antioxidant and anti-hypertensive effects.
Gamma-aminobutyric acid (GABA) has many pharmacological functions including being a major inhibitory neurotransmitter. Two comparative methods for GABA production in rice grains as main food source in Thailand were investigated in this study. Fermentation and germination method were separately carried out using seven selected local grain cultivars in northern Thailand. Red yeast rice, obtained from the fermentation method, gave the higher GABA concentration than the germinated rice produced from the germination method in most rice cultivars. The highest GABA concentration was 28.37 mg/ g at 3 weeks fermentation time of glutinous rice, O. sativa L. cv. Sanpatong 1 cultivars, while germinated rice from glutinous rice; O. sativa L. cv. Korkor6 (RD6) cultivars contained the highest GABA concentration of 3.86 mg/g. These results provide information for the basis of an appropriate method for GABA production. The fermentation produced higher GABA concentration but required longer production period and red yeast rice was obtained as product. On the other hand, the germination method yielded rice grains with lower GABA but in more suitable form for consumption. Both methods are considered to be economical and efficient methods to increase GABA in rice grains, providing alternative products with higher nutritional values.
Red yeast rice which is a product of solid fermentation was prepared from several kinds of Thai glutinous rice (Oryza sativa L.) cv. Korkor 6 (RD6), Kam (Kam), and Sanpatong1 (SPT1). Monascus purpureus CMU001 isolated from available Chinese red yeast rice was used as the fermentation starter. The analysis for the presence and the content of monacolins, the cholesterollowering compounds, were carried out using high performance liquid chromatography (HPLC). The presence of the monacolins was confirmed by the retention time of the reference compounds and LC-MS. The results were compared to those obtained from the Chinese red yeast rice and Thai non-glutinous rice (O. sativa L. cv. Mali105). The chromatograms show the presence of monacolin K acid form (MKA), compactin (P1), monacolin M acid form (MMA), monacolin K (MK), monacolin M (MM), and dehydromonacolin K (DMK). A large peak of a compound with the molecular weight of 358 was also detected but could not be identified. The amount of two important monacolins, compactin, and monacolin K, were determined. It was found that the highest amount of compactin and monacolin K were 21.98 and 33.79 mg/g, respectively, when using Thai rice varity O. sativa L. cv. RD6 which was fermented without adding soybean milk.
Membranes prepared by drying aqueous Bombyx mori silk fibroin (SF) solution and modified silk fibroin (MSF) solutions, prepared by adding the low molecular weight crosslinking agent, polyethylene glycol diglycidyl ether (PEGDE) MW 526, 0-10% w/w, were investigated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and UV-vis spectroscopy. Weight gain in aqueous solutions and their mechanical properties (tensile strength, elongation, and Young's modulus) were then characterized. SEM measurements revealed greater porosity in MSF membranes. IR spectra showed transformation from the largely a-helical/ random coil structures in SF membranes to predominantly b-sheet in MSF membranes. Results from UV-vis spectroscopy showed that the MSF membranes were largely insoluble within the pH range of 4-10. Water absorbability of the MSF membranes improved with increasing the amounts of cross-linker, up to 4%. The MSF membranes showed greater pliability and tenacity, but lower tensile strength, with increasing PEGDE concentrations. In the wet condition, PEGDE levels up to 4% can improve both tensile strength and tenacity of the MSF membrane, but higher levels (up to 10%) did not significantly change these properties.
Abstract-The bird chili powder (Capsicum frutescens Linn.) was a source of aflatoxigenic fungus which was identified as Aspergillus flavus. The antagonist Bacillus subtilis BCC 6327 was shown to inhibit the growth and spore germination of the isolated aflatoxigenic fungus from bird chili powder. All the cell free supernatant from 12, 24 and 36 h of incubation could inhibit the growth and mycelium production with inhibition percentages of 92.1, 89.6 and 90.1%, respectively. Growth of aflatoxigenic fungi was inversely correlated with enzyme productions from B. subtilis. Productions of protease, chitinase and β-1,3-glucanase and the released sugars (total reducing sugar, glucose and N-acetylglucosamine) were enhanced by the dried fungal mycelia. B. subtilis culture filtrates, possessing protease, chitinase and β-1, 3-glucanase, were capable of hydrolyzing dried mycelia of the isolated aflatoxigenic fungi from bird chili powder.
Fish skin, one type of wastes generated from Nile tilapia processing, is still a good source of collagen and gelatin. Bioactive peptides can be obtained from Nile tilapia skin gelatin by trypsin digestion. Trypsin hydrolysate was subsequently purified by gel filtration chromatography. Trypsin A fraction showed the greatest reducing power (5.138 ± 1.060 μM trolox/mg peptide) among all hydrolysate fractions, while trypsin B fraction from gel filtration column was found to exhibit the best radical scavenging and angiotensin-I-converting enzyme (ACE) inhibitory activities 8.16 ± 2.18 μg trolox/mg peptide and 59.32 ± 9.97 % inhibition, respectively. The most active fraction was subjected to MALDI-TOF/TOF MS/MS. After annotation by Mascot sequence matching software (Matrix Science) with Ludwig NR Database, two peptide sequences were identified; GPEGPAGAR (MW 810.87 Da) and GETGPAGPAGAAGPAGPR (MW 1490.61 Da). The docking analysis suggested that the shape of the shorter peptide may be slightly more proper, to fit into the binding cleft of the ACE. However, the binding affinities calculated from the docking showed no significant difference between the two peptides. In good agreement with the in silico data, results from the in vitro ACE inhibitory activity with synthetic peptides also showed no significant difference. Both peptides are thus interesting novel candidates suitable for further development as ACE inhibitory and antioxidant agents from the natural source.
A myrosinase (thioglucoside glucohydrolase or thioglucosidase, EC 3.2.3.147) producing fungus, Aspergillus sp. NR4617, was newly isolated from decayed soil sample obtained in Thailand and was subjected to single exposure to two chemical mutagens, ethyl methanesulfonate (EMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Its myrosinase production was selected on low cost medium prepared from mustard seed cake (Brassica juncea). Studies of production and stability of the enzyme showed that EMS mutagenesis increased myrosinase activity. Aspergillus sp. NR4617E1 produced myrosinase 1.90 U ml -1 at 36 hrs of the cultivation equivalent to 171% of the enzyme production in wild-type. The stability studies revealed that myrosinase from the mutant strains retained activity similar to wild-type at 30ºC. Aspergillus sp. NR4617E1 degraded 10 mM of glucosinolate completely in 36 hrs. Enhanced myrosinase production and high yields of products (allylisothiocyanate) demonstrated that this mutant could be a new found candidate for feed detoxification and industrial allylisothiocyanate production.Myrosinase (thioglucoside glucohydrolase EC 3.2.3.147) is found in all glucosinolate containing plants such as Brassicaseae (o Brassicaceae) in some bacteria and fungi (Rask et al. 2000). Myrosinase is normally segregated from glucosinolates, sugar anionic thioesters containing betathioglucolate glycoside bonds, in plant tissues (Brown and
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