The present study focused on developing a wild-type actinomycete isolate as a model for a non-pathogenic filamentous producer of biosurfactants. A total of 33 actinomycetes isolates were screened and their extracellular biosurfactants production was evaluated using olive oil as the main substrate. Out of 33 isolates, 32 showed positive results in the oil spreading technique (OST). All isolates showed good emulsification activity (E24) ranging from 84.1 to 95.8%. Based on OST and E24 values, isolate R1 was selected for further investigation in biosurfactant production in an agitated submerged fermentation. Phenotypic and genotypic analyses tentatively identified isolate R1 as a member of the Streptomyces genus. A submerged cultivation of Streptomyces sp. R1 was carried out in a 3-L stirred-tank bioreactor. The influence of impeller tip speed on volumetric oxygen transfer coefficient (kLa), growth, cell morphology and biosurfactant production was observed. It was found that the maximum biosurfactant production, indicated by the lowest surface tension measurement (40.5 ± 0.05 dynes/cm) was obtained at highest kLa value (50.94 h−1) regardless of agitation speed. The partially purified biosurfactant was obtained at a concentration of 7.19 g L−1, characterized as a lipopeptide biosurfactant and was found to be stable over a wide range of temperature (20–121 °C), pH (2–12) and salinity [5–20% (w/v) of NaCl].
Ethyl levulinate (EL) is a versatile bio-based chemical with various applications such as fragrance and flavoring agents and also fuel blending component. EL can be produced through catalytic esterification of levulinic acid (LA) with ethanol. Herein, a series of zirconia (ZrO2)-supported phosphotungstic acid (HPW) (HPW/Zr) catalyst, 15-HPW/Zr, 20-HPW/Zr, and 25-HPW/Zr, were prepared, characterized, and tested for EL production. The physicochemical properties of catalysts were characterized using Fourier-transformed infrared (FTIR) spectroscopy, x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), N2 physisorption, and ammonia temperature-programmed desorption (NH3-TPD). The effect of reaction parameters: reaction time, temperature, catalyst loading, and molar ratio of LA to ethanol was inspected on LA conversion and EL yield. The catalyst with high surface area and high acidity seemed suitable for EL production. Among the catalysts tested, 20-HPW/Zr exhibited the highest EL yield of 97.3% at the following conditions: 150 °C, 3 h, 1.0 g of 20-HPW/Zr and 1:17 M ratio of LA to ethanol. The 20-HPW/Zr could be reused for at least four times with insignificant decrease in the EL yield. This study demonstrates the potential of ZrO2-supported HPW for bio-based alkyl levulinate production at mild process conditions. 相似文献
Levulinic acid (LA) is a versatile platform chemical that can be derived from biomass as an alternative to fossil fuel resources. Herein, the optimization of LA production from glucose and oil palm fronds (OPF) catalyzed by an acidic ionic liquid; 1-sulfonic acid-3-methyl imidazolium tetrachloroferrate ([SMIM][FeCl4]) have been investigated. Response surface methodology based on Box-Behnken design was employed to optimize the LA yield and to examine the effect and interaction of reaction parameters on the LA production. The reaction parameters include reaction temperature, reaction time, feedstock loading, and catalyst loading. From the optimization study, the predicted mathematical models for LA production from glucose and OPF covered more than 90 % of the variability in the experimental data. At optimum conditions, 69.2 % of LA yield was obtained from glucose, while 24.8 % of LA yield was attained from OPF and registered 77.3 % of process efficiency. The recycled [SMIM][FeCl4] gave sufficient performance for five successive cycles. Furthermore, the optimum LA produced from glucose and OPF can be directly converted to ethyl levulinate through esterification over the [SMIM][FeCl4] catalyst. This study highlights the potential of [SMIM][FeCl4] for biorefinery processing of renewable feedstocks at mild process conditions. 相似文献
Recently, certain lots of heparin have been associated with an acute, rapid onset of serious side effects indicative of an allergic-type reaction. To identify potential causes for this sudden rise in side effects, we examined lots of heparin that correlated with adverse events using orthogonal high-resolution analytical techniques. Through detailed structural analysis, the contaminant was found to contain a disaccharide repeat unit of glucuronic acid linked beta1-->3 to a beta-N-acetylgalactosamine. The disaccharide unit has an unusual sulfation pattern and is sulfated at the 2-O and 3-O positions of the glucuronic acid as well as at the 4-O and 6-O positions of the galactosamine. Given the nature of this contaminant, traditional screening tests cannot differentiate between affected and unaffected lots. Our analysis suggests effective screening methods that can be used to determine whether or not heparin lots contain the contaminant reported here. 相似文献
Summary The lysine biosynthetic genes asd, dapA, and dapB, encoding aspartate semialdehyde dehydrogenase (ASADH), dihydrodipicolinate synthase (DHPS), and dihydrodipicolinate reductase
(DHPR), respectively, have been cloned from Lactobacillus plantarum IAM 12477 by heterologous complementation to Escherichia coli mutants. The amino acid sequences of the cloned genes showed considerable similarities to the corresponding protein from
other gram-positive bacteria. We identified the amino acids that correspond to key catalytic residues of ASADH, DHPS, and
DHPR and found them to be conserved in the protein from L. plantarum. ASADH, DHPS, and DHPR activity was detected in the cell extracts of E. coli mutant harboring each gene, indicating that the cloned genes were functionally expressed in E. coli. The regulation of ASADH, DHPS, and DHPR were studied in the cell extracts of both the E.␣coli mutant harboring the gene and L. plantarum; however, those enzymes were found not to be regulated by the end products of the pathway.
This paper represents a portion of the thesis submitted by M. N. Cahyanto to Osaka University as partial fulfillment of the
requirements for the PhD degree. 相似文献
Many species of Dipterocarpaceae and other plant families reproduce synchronously at irregular, multi‐year intervals in Southeast Asian forests. These community‐wide general flowering events are thought to facilitate seed survival through satiation of generalist seed predators. During a general flowering event, closely related Shorea species (Dipterocarpaceae) stagger their flowering times by several weeks, which may minimize cross pollination and interspecific competition for pollinators. Generalist, pre‐dispersal seed predators might also track flowering hosts and influence predator satiation. We addressed the question of whether pre‐dispersal seed predation differed between early and late flowering Shorea species by monitoring flowering, fruiting and seed predation intensity over two general flowering events at the Pasoh Research Forest, Malaysia. Pre‐dispersal insect seed predators killed up to 63 percent of developing seeds, with Nanophyes shoreae, a weevil that feeds on immature seeds being the most important predator for all Shorea species. This weevil caused significantly greater pre‐dispersal seed predation in earlier flowering species. Long larval development time precluded oviposition by adults that emerged from the earliest flowering Shorea on the final flowering Shorea. In contrast, larvae of weevils that feed on mature seeds before seed dispersal (Alcidodes spp.), appeared in seeds of all Shorea species almost simultaneously. We conclude that general flowering events have the potential to satiate post‐dispersal seed predators and pre‐dispersal seed predators of mature fruit, but are less effective at satiating pre‐dispersal predators of immature fruit attacking early flowering species. 相似文献
Starch within the endosperm of most species of the Triticeae has a unique bimodal granule morphology comprising large lenticular A-type granules and smaller near-spherical B-type granules. However, a few wild wheat species (Aegilops) are known to lack B-granules. Ae. peregrina and a synthetic tetraploid Aegilops with the same genome composition (SU) were found to differ in B-granule number. The synthetic tetraploid had normal A- and B-type starch granules whilst Ae. peregrina had only A-granules because the B-granules failed to initiate. A population segregating for B-granule number was generated by crossing these two accessions and was used to study the genetic basis of B-granule initiation. A combination of Bulked Segregant Analysis and QTL mapping identified a major QTL located on the short arm of chromosome 4S that accounted for 44.4% of the phenotypic variation. The lack of B-granules in polyploid Aegilops with diverse genomes suggests that the B-granule locus has been lost several times independently during the evolution of the Triticeae. It is proposed that the B-granule locus is susceptible to silencing during polyploidization and a model is presented to explain the observed data based on the assumption that the initiation of B-granules is controlled by a single major locus per haploid genome. 相似文献
Ultraviolet radiation (UV) from sunlight is the primary cause of skin and ocular neoplasia. Brahma (BRM) is part of the SWI/SNF chromatin remodeling complex. It provides energy for rearrangement of chromatin structure. Previously we have found that human skin tumours have a hotspot mutation in BRM and that protein levels are substantially reduced. Brm−/− mice have enhanced susceptibility to photocarcinogenesis. In these experiments, Brm−/− mice, with both or a single Trp53 allele were exposed to UV for 2 or 25 weeks. In wild type mice the central cornea and stroma became atrophic with increasing time of exposure while the peripheral regions became hyperplastic, presumably as a reparative process. Brm−/−, Trp53+/−, and particularly the Brm−/− Trp53+/− mice had an exaggerated hyperplastic regeneration response in the corneal epithelium and stroma so that the central epithelial atrophy or stromal loss was reduced. UV induced hyperplasia of the epidermis and corneal epithelium, with an increase in the number of dividing cells as determined by Ki-67 expression. This response was considerably greater in both the Brm−/− Trp53+/+ and Brm−/− Trp53+/− mice indicating that Brm protects from UV-induced enhancement of cell division, even with loss of one Trp53 allele. Cell division was disorganized in Brm−/− mice. Rather than being restricted to the basement membrane region, dividing cells were also present in the suprabasal regions of both tissues. Brm appears to be a tumour suppressor gene that protects from skin and ocular photocarcinogenesis. These studies indicate that Brm protects from UV-induced hyperplastic growth in both cutaneous and corneal keratinocytes, which may contribute to the ability of Brm to protect from photocarcinogenesis. 相似文献
Chronic kidney disease is an emerging problem in the majority Muslim countries. Despite the uncertainties of the risks involved, some Muslim patients undergoing chronic haemodialysis choose to observe intermittent fasting during the month of Ramadan. This study aims to investigate the effect of Ramadan fasting in haemodialysis patients residing in a tropical climate country.
Methods
This prospective cross sectional study recruited Muslim patients on regular haemodialysis from three haemodialysis centres in Kuala Lumpur from 15th July 2011 to 29th August 2011. Patients who fasted for any number of days were included (n = 35, 54% female, age 54±11 years). 89% of patients fasted for more than 15 days and 49% were diabetics. Dialysis parameters and blood samples were obtained one week prior to Ramadan and during the last week of Ramadan. The differences in dialysis parameters and biochemical values pre- and end-Ramadan were examined using paired t-test.
Results
Both pre- and post-dialysis weight were significantly decreased during Ramadan fasting compared to the month prior (p = <0.001). There was a significant decrease in the amount of ultrafiltration (p = 0.002). There were no significant differences in dry weight, inter-dialytic weight gain, mean urea reduction ratio or blood pressure measurements comparing pre- and end of Ramadan fasting. There was a significant increase in serum albumin level (p = 0.006) and decrease in serum phosphate level (p = 0.02) at the end of Ramadan.
Conclusion
Ramadan fasting is associated with reduced weight, improved serum albumin and phosphate level in our population of haemodialysis patients. A larger multi-centre study will allow us to understand more about the effects of fasting in this population. 相似文献