Studies on tuber starches III. Impact of annealing on the molecular structure,composition and physicochemical properties of yam (Dioscorea sp.) starches grown in Sri Lanka

This study reports the impact of one step annealing on the composition, molecular structure, granule morphology and physicochemical properties of starches isolated from cultivars of Dioscorea esculenta (kukulala, java-ala-nattala) and Dioscorea alata (hingurala, raja-ala), yam tubers grown in Sri Lanka. In all starches, granule morphology (shape, size, surface appearance), birefringence patterns, acid hydrolysis profile and X-ray patterns remained unchanged on annealing. Crystallinity remained unchanged on annealing in hingurala, kukulala and java-ala. However, crystallinity of raja-ala and nattala increased and decreased, respectively, on annealing. In all starches, annealing decreased the gelatinization temperature range (kukulala ～ hingurala > nattala ～ raja-ala > java-ala), amylose leaching (raja-ala > nattala > hingurala > kukulala > java-ala), granular swelling (raja-ala ～ hingurala > kukulala > java-ala > nattala), peak viscosity (raja-ala > hingurala > kukulala > java-ala > nattala), enthalpy of retrogradation (kukulala ～ java-ala ～ nattala ～ hingurala ～ raja-ala) and susceptibility towards acid hydrolysis (java-ala > raja-ala > hingurala ～ nattala > kukulala). However, annealing increased gelatinization temperatures (kukulala ～ java-ala ～ nattala ～ raja-ala ～ hingurala) and the enthalpy of gelatinization (kukulala > hingurala > java-ala > nattala > raja-ala). Set-back viscosity increased in nattala, but decreased in the other starches (raja-ala > hingurala > kukulala > java-ala) on annealing. The study showed that the different responses shown by the cultivars of the Dioscorea starches towards annealing were to a large extent influenced by their composition and molecular structure.     

Identification of glycolaldehyde as the key inhibitor of bioethanol fermentation by yeast and genome-wide analysis of its toxicity

Degradation of lignocellulose with pressurised hot water is an efficient method of bioethanol production. However, the resultant solution inhibits ethanol fermentation by Saccharomyces cerevisiae. Here, we first report that glycolaldehyde, which is formed when lignocellulose is treated with pressurised hot water, inhibits ethanol fermentation. The final concentration of glycolaldehyde formed by the treatment of lignocellulose with pressurised hot water ranges from 1 to 24 mM, and 1–10 mM glycolaldehyde was sufficient to inhibit fermentation. This result indicates that glycolaldehyde is one of the main substances responsible for inhibiting fermentation after pressurised hot water degradation of lignocellulose. Genome-wide screening of S. cerevisiae revealed that genes encoding alcohol dehydrogenase, methylglyoxal reductase, polysomes, and the ubiquitin ligase complex are required for glycolaldehyde tolerance. These novel findings will provide new perspectives on breeding yeast for bioethanol production from biomass treated with pressurised hot water.     

Loss of Fgfr2 leads to partial XY sex reversal

In mammals, sex is determined in the bipotential embryonic gonad by a balanced network of gene actions which when altered causes disorders of sexual development (DSD, formerly known as intersex). In the XY gonad, presumptive Sertoli cells begin to differentiate when SRY up-regulates SOX9, which in turn activates FGF9 and PGDS to maintain its own expression. This study identifies a new and essential component of FGF signaling in sex determination. Fgfr2 mutant XY mice on a mixed 129/C57BL6 genetic background had either normal testes, or developed ovotestes, with predominantly testicular tissue. However, backcrossing to C57BL6 mice resulted in a wide range of gonadal phenotypes, from hypoplastic testes to ovotestes with predominantly ovarian tissue, similar to Fgf9 knockout mice. Since typical male-specific FGF9-binding to the coelomic epithelium was abolished in Fgfr2 mutant XY gonads, these results suggest that FGFR2 acts as the receptor for FGF9. Pgds and SOX9 remained expressed within the testicular portions of Fgfr2 mutant ovotestes, suggesting that the Prostaglandin pathway acts independently of FGFR2 to maintain SOX9 expression. We could further demonstrate that double-heterozygous Fgfr2/Sox9 knockout mice developed ovotestes, demonstrating that both Fgfr2 and Sox9 can act as modifier intersex genes in the heterozygous state. In summary, we provide evidence that FGFR2 is important for male sex determination in mice, thereby rendering human FGFR2 a candidate gene for unsolved DSD cases such as 10q26 deletions.     

Evaluating Spatial and Temporal Variability of Fecal Coliform Bacteria Loads at the Pelahatchie Watershed in Mississippi

Bacterial contaminations of surface waters are an increasing concern for scientists and public health agencies because pathogenic bacteria can cause adverse effects on human health. This research was performed to investigate spatial and seasonal variability of fecal coliform bacteria (FCB) concentrations in the Pelahatchie watershed (527 km²) in Mississippi, USA. Livestock manure, poultry litter, and effluent from failing septic systems were identified as major sources of FCB in the Pelahatchie watershed. The Soil and Water Assessment Tool (SWAT)/microbial sub-model was applied, and model-simulated FCB concentrations were compared with the monthly measured FCB concentrations (years 2001–2008) at the outlet of the watershed. New methodologies were introduced to incorporate bacteria loads into the bacteria model. Results showed coefficients of determination (R ²) of 0.71 to 0.75, and Nash-Sutcliffe efficiency index (NSE) of 0.67 to 0.75 during the bacteria model's calibration and validation periods, respectively. Seasonal analysis of the model-simulated results determined the highest bacteria concentrations in January, whereas the lowest concentrations were simulated in June. Furthermore, the FCB contributions to the watershed outlet from the sources of contamination varied with time of year. This study will help watershed managers to implement best management practices for improvement of water quality.     

Antidiuretic activity of aqueous bark extract of Sri Lankan Ficus racemosa in rats

The decoction (D) of the bark of Ficus racemosa Linn (Family: Moraceae) is claimed as an antidiuretic by some Sri Lankan traditional practitioners. However, the validity of this claim has not been scientifically proven or refuted. The aim of this study was to evaluate the antidiuretic potential of D of the bark of F. racemosa (made as specified in traditional use) in rats using three doses (250, 500 or 1000 mg/kg) following oral administration. The reference drug used was ADH. The results demonstrated both the low- and high-doses of D and ADH significantly impaired the total urine output. The D-induced antidiuresis had a rapid onset (within 1 h), peaked at 3 h and lasted throughout the study period (5 h). However, antidiuretic potential of D was about 50% lower than that of ADH. The D was well tolerated even with subchronic administration. The D caused a reduction in urinary Na+ level and Na+/K+ ratio, and an increase in urinary osmolarity indicating multiple mechanisms of action. The results provide scientific support for its claimed antidiuretic action and deserve intensive scrutiny.     

Cholesterol feeding impairs endothelium-dependent relaxation of rabbit aorta

Experiments were designed to assess the effect of cholesterol feeding on the endothelium-mediated relaxation of the rabbit aorta to acetylcholine. Age-matched male New Zealand white rabbits were fed either a 2% cholesterol diet or standard rabbit chow. The animals were anaesthetized with sodium pentobarbitone and sacrificed after 4 and 8 weeks on these diets. Rings were prepared from the proximal thoracic aorta and examined in tissue baths. These rings were contracted first with norepinephrine (-6 log mol/L) and acetylcholine was added to demonstrate the endothelium-mediated relaxation. The endothelium-dependent relaxation was significantly less in aortas from rabbits fed the 2% cholesterol diet than in aortas from animals fed the conventional diet. This impairment of relaxation was apparent after both 4 and 8 weeks of cholesterol feeding. In both groups of animals no relaxation was seen in rings from which the endothelium was removed. These results show that cholesterol feeding leads to an impairment of endothelium-mediated relaxation of the rabbit aorta to acetylcholine.     

Endothelium-dependent relaxation and experimental atherosclerosis in the rabbit aorta

This study was undertaken to determine whether the production or release of the endothelium-dependent relaxatory factor is impaired in atherosclerotic New Zealand White rabbits. Atherosclerosis was induced by feeding a diet containing 2% cholesterol for 6 weeks. The production or release of endothelium-dependent relaxatory factor was assayed as follows. A 5-cm length of aorta donor was perfused with Krebs-bicarbonate buffer and the perfusate drained over a deendothelialized ring of recipient aorta set up for recording isometric tension. The recipient was precontracted with norepinephrine (0.2 mumol/L) in the perfusate. When acetylcholine was added to the perfusate, the recipient relaxed in a dose-dependent manner. This assay was used to compare the relaxatory responses produced in recipient rings by adding acetylcholine to donors from atherosclerotic and control rabbits. The relaxation produced by atherosclerotic donors were smaller than those generated by control donors (16.5 +/- 4.9 vs. 32.7 +/- 5.3%; n = 10, p less than 0.05). It is suggested that in atherosclerotic rabbits the ability of aortic endothelium to produce or release endothelium-dependent relaxatory factor is impaired.     

Identification and detoxification of glycolaldehyde,an unattended bioethanol fermentation inhibitor

Although there have been approximately 60 chemical compounds identified as potent fermentation inhibitors in lignocellulose hydrolysate, our research group recently discovered glycolaldehyde as a key fermentation inhibitor during second generation biofuel production. Accordingly, we have developed a yeast S. cerevisiae strain exhibiting tolerance to glycolaldehyde. During this glycolaldehyde study, we established novel approaches for rational engineering of inhibitor-tolerant S. cerevisiae strains, including engineering redox cofactors and engineering the SUMOylation pathway. These new technical dimensions provide a novel platform for engineering S. cerevisiae strains to overcome one of the key barriers for industrialization of lignocellulosic ethanol production. As such, this review discusses novel biochemical insight of glycolaldehyde in the context of the biofuel industry.