Unripe Fruit's Extract of Quince (Cydonia oblonga Miller) as a Potent Alpha-amylase Inhibitor

The use of alpha-amylase inhibitors has recently gained in popularity with the success and growth of carbohydrate restricted diets. In this study, two different stages from the unripe fruits of quince (Cydonia oblonga Miller) have been tested for their potentiality in alpha-amylase inhibition as a key enzyme in carbohydrates assimilation. Our results revealed that addition of different concentrations from extracts (0, 2, 4, 6, 8mg) of dry mass of each stage of unripe fruits resulted in drastically decrease in the enzymatic activity of alpha-amylase by the percent of (0%, 42.6%, 21%, 26.3%, and 16.9%) for the stage 1. Extracts from the stage 2 were more effective in enzymatic inhibition (0%, 26.9%, 3.8%, 0.2%, and 0.4%). The GC/MS analysis revealed that quince extract contains (sorbitol, quinic acid, p-vinylphenol and cyclopropane carboxylic acid). To explore which components are involved in the inhibition process, two pure components of the quince extract (sorbitol and quinic acid) were used in inhibition assay. Neither sorbitol nor quinic acid shows any significant inhibition; therefore, these two components could be excluded from the inhibition process. Our current study suggested that p-vinylphenol and cyclopropane carboxylic acid might act as a-amylase inhibitors in vitro separately or synergistically. The possible explanation for the presence of cyclopropane carboxylic acid (CPCA) in this critical phase of the unripe fruit will be discussed. This study suggests that the unripe fruits of quince can be used as a natural starch blocker containing alpha-amylase inhibitors which would be of interest for people requiring carbohydrate restricted diets

シアノバクテリアにおけるフェレドキシンーNADP[+]酸化還元酵素および耐熱性グルコシダーゼの生化学的研究

取得学位：博士(理学)，学位授与番号：博甲第959号，学位授与年月日：平成19年9月28

Bioconversion of plant wastes to β-carotene by Rhodotorula glutinis KU550702

Microbial synthesis of β-carotene has gained more interest as an alternative to synthetic β-carotene due to easy extraction and high yield. The vitamin microbial production is mainly dependent on culture conditions and the medium compositions. In this study, the β-carotene production by the Rhodo-torula glutinis ASU6 (KU550702) was evaluated under different growth conditions and nutrient composition. Different agro-renewable wastes were tested as carbon source for R. glutinis to obtain maximum amount of β-carotene. Meanwhile, it is clear that R. glutinis could grow well on acid extract of onion peels and produced large amount of β-carotene. Initial statistical screening using a Plackett-Burman design showed temperature, incubation time, fermentation type, non-treated onion waste, KH2PO4 and L-asparagine as significantly, influencing β-carotene production. Response surface methodology was applied to determine the mutual interactions between these parameters and optimal levels for β-carotene production. The maximum value of β-carotene production was 204.29 mg/l (7.5-fold) of value observed as central point of the central composite design. All the experimental data are in good agreement with predicted ones, confirming the responsibility of the proposed empirical model in describing β-carotene production by R. glutinis. In the whole, the outcomes of this study support the exploitation of onion peels through microbial fermentation for β-carotene production

Optimization of Extracellular Keratinase Production by Aspergillus terreus Isolated from Chicken's Litter

In this current study 45 fungal isolates were isolated from chicken's litter on Feather Agar Medium (FAM) were screened for determining the potent keratinase producing isolates. Out of these fungal isolates, twelve species and one species variety exhibited various degrees of keratinolytic activities from which A. terreus showed the highest keratinase production (12.6U/ml). The optimum temperature and initial pH for keratinase production by A. terreus were 40°C and 8, respectively. The highest keratinase production was observed for a period 25 days. The optimum ionic strength for the enzyme production was 80mM NaCl. Deprivation of K+, Fe2+, Mg2+, Ca2+ or Zn2+ from the culture medium drastically reduced the keratinase production by A. terreus. In contrast, sulfur deprivation did not significantly affect the keratinase production. The Km and Vmax values for A. terreus keratinase were 8.64mg keratin and 56.7U/mg proteins, respectively. The optimum temperature, pH and ionic strength for keratinase activity were 35°C, 7.8 and 80-100mM NaCl, respectively

A simple approach to water and plankton sampling for water microbiological and physicochemical characterizations at various depths in aquatic ecosystems

Water microbiological and physicochemical characterizations at various depths of aquatic ecosystems are basic requirements in several fields of research. A chief difficulty in hydrobiology, limnology, biological oceanography and water environmental microbiology is that of taking accurate field collections that are representative of the natural environment and population at various depths of aquatic ecosystems. Gathering water/plankton samples in a level just below the surface of the water body upon rising in columns from various depths due to hydrostatic pressure variations provided a simple approach for water and plankton sampling. Based on this approach, several forms of simple devices for water and plankton sampling were developed for water microbiological and physicochemical characterizations at various depths of aquatic ecosystems. The described approach showed less sampling errors in comparison to Van Dorn bottle and was comparable to water pumping but requires no external source of power. The described samplers are inexpensive and can be self constructed

Semidry acid hydrolysis of cellulose sustained by autoclaving for production of reducing sugars for bacterial biohydrogen generation from various cellulose feedstock

Cellulosic biowastes are one of the cheapest and most abundant renewable organic materials on earth that can be, subsequent to hydrolysis, utilized as an organic carbon source for several fermentation biotechnologies. This study was devoted to explore a semidry acid hydrolysis of cellulose for decreasing the cost and ionic strength of the hydrolysate. For semidry acid hydrolysis, cellulose was just wetted with HCl (0 to 7 M) and subjected to autoclaving. The optimum molar concentration of HCl and period of autoclaving for semidry acid hydrolysis of cellulose were 6 M and 50 min respectively. Subsequent to the semidry acid hydrolysis with a minimum volume of 6 M HCl sustained by autoclaving, the hydrolysate was diluted with distilled water and neutralized with NaOH (0.5 M). The reducing sugars produced from the semidry acid hydrolysis of cellulose was further used for dark fermentation biohydrogen production by Escherichia coli as a representative of most hydrogen producing eubacteria which cannot utilize non-hydrolyzed cellulose. An isolated E. coli TFYM was used where this bacterium was morphologically and biochemically characterized and further identified by phylogenetic 16S rRNA encoding gene sequence analysis. The reducing sugars produced by semidry acid hydrolysis could be efficiently utilized by E. coli producing 0.4 mol H2 mol−1 hexose with a maximum rate of hydrogen gas production of 23.3 ml H2 h−1 L−1 and an estimated hydrogen yield of 20.5 (L H2 kg−1 dry biomass). The cheap cellulosic biowastes of wheat bran, sawdust and sugarcane bagasse could be hydrolyzed by semidry acid hydrolysis where the estimated hydrogen yield per kg of its dry biomass were 36, 18 and 32 (L H2 kg−1 dry biomass) respectively indicating a good feasibility of hydrogen production from reducing sugars prepared by semidry acid hydrolysis of these cellulosic biowastes. Semidry acid hydrolysis could also be effectively used for hydrolyzing non-cellulosic polysaccharides of dry cyanobacterial biomass. The described semidry acid hydrolysis of cellulosic biowastes in this study might be applicable not only for bacterial biohydrogen production but also for various hydrolyzed cellulose-based fermentation biotechnologies

Novel thermostable glycosidases in the extracellular matrix of the terrestrial cyanobacterium Nostoc commune

The cyanobacterium Nostoc commune is adapted to the terrestrial environment and forms a visible colony in which the cells are embedded in extracellular polysaccharides (EPSs), which play a crucial role in the extreme desiccation tolerance of this organism. When natural colonies were immersed in water, degradation of the colonies occurred within 2 days and N. commune cells were released into the water. The activities that hydrolyze glycoside bonds in various N. commune fractions were examined using artificial nitrophenyl-linked sugars as substrates. A β-D-glucosidase purified from the water-soluble fraction was resistant to 20 min of boiling. The β-D-glucosidase, with a molecular mass of 20 kDa, was identified as a cyanobacterial fasciclin protein based on its N-terminal amino-acid sequence. The 36-kDa major protein in the water-soluble fraction was purified, and the N-terminal amino-acid sequence of the protein was found to be identical to that of the water-stress protein (WspA) of N. commune. This WspA protein also showed heat-resistant β-D-galactosidase activity. The fasciclin protein and WspA in the extracellular matrix may play a role in the hydrolysis of the EPSs surrounding the cells, possibly as an aid in the dispersal of cells, thus expanding the colonies of this cyanobacterium