Optimization of nutritional requirements and ammonium feeding strategies for improving vitamin B12 production by Pseudomonas denitrificans

Statistical experiment design and data analysis were used to establish the major factors in a chemically defined medium and to develop an ammonium control strategy to optimize the specific vitamin B12 production rate (Yp) of Pseudomonas denitrificans. Through Plackett-Burman design, the major factors of glucose, ammonium sulfate and KCl were selected as the significant factors affecting vitamin B12 biosynthesis and these were further optimized by central composite design with response surface methodology. The maximum Yp of 34.2 μg/gDCW/h was obtained in batch cultivation under the estimated optimal initial composition of glucose (93.6 g/l), (NH4)2SO4 (7.93 g/l) and KCl (1.24 g/l). Ammonium control strategies in fed-batch fermentation showed that when ammonium concentration was maintained at 40 mmol/l, the maximum Yp reached 36.0 ± 1.31 μg/gDCW/h, which was 57.2% higher than that of the control (22.9 ± 0.83 μg/gDCW/h). This ammonium control strategy successfully enhanced the industrial production, resulting in a stable high vitamin B12 production of 212.02 ± 3.03 mg/l and Yp of 37.1 μg/gDCW/h.Key words: Statistical designs, Pseudomonas denitrificans, chemically defined medium, ammonium controlling strategy, vitamin B12

Double-stranded break can be repaired by single-stranded oligonucleotides via the ATM/ATR pathway in mammalian cells

Single-stranded oligonucleotide (SSO)-mediated gene modification is a newly developed tool for site-specific gene repair in mammalian cells; however, the corrected cells always show G2/M arrest and cannot divide to form colonies. This phenomenon and the unclear mechanism seriously challenge the future application of this technique. In this study, we developed an efficient SSO-mediated DNA repair system based on double-stranded break (DSB) induction. We generated a mutant EGFP gene with insertions of 24 bp to 1.6 kb in length as a reporter integrated in mammalian cell lines. SSOs were successfully used to delete the insertion fragments upon DSB induction at a site near the insertion. We demonstrated that this process is dependent on the ATM/ATR pathway. Importantly, repaired cell clones were viable. Effects of deletion length, SSO length, strand bias, and SSO modification on gene repair frequency were also investigated. © 2008 Mary Ann Liebert, Inc.published_or_final_versio

Characteristics and community diversity of a wheat straw-colonizing microbial community

A microbial community named WSD-5 was successfully selected from plant litter and soil after longterm directed acclimation at normal temperature. After 15 days of cultivation at 30°C, the degradation rate of wheat straw by WSD-5 was 75.6%. For cellulose, hemicellulose and lignin, the degradation rates were 94.2, 81.9 and 21.3%, respectively. The optimal pH for filter paper, CMCase, avicelase, β- glucosidase and xylanse activities was 6.24, 6.24, 5.91, 5.91 and 6.24, respectively. The optimal reaction temperature for all enzyme activity was 55°C. Filter paper enzyme, cellulase and xylanase were secreted from the degradation of wheat straw by WSD-5. The highest filter paper, cellulose endonuclease (CMCase), cellulose exonuclease (avicelase), β-glucosidase and xylanase activities were 1.30, 4.35, 0.60, 0.43 and 15.16 U/ml, respectively. A library of bacterial and fungal ribosomal gene sequences obtained from the community showed the presence of Ochrobactrum sp, Coprinus cinereus and Pseudallescheria boydii. To our knowledge, this was the first report of a microbial community which consisted of bacteria and fungi and was selected in the presence of wheat straw to produce extracellular filter paper enzyme, cellulase and xylanase.Key words: Microbial community, lignocellulose degradation, filter paper activity, CMCase, avicelase, β- glucosidase, xylanase

An emigration genetic algorithm and its application to multiobjective optimal designs of electromagnetic devices

Author name used in this publication: S. L. Ho2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Utilization of dental services in Southern China

A population's utilization of dental services is an important parameter in oral health care planning, which has rarely been studied in China. The objectives of this report were to describe the dental service utilization pattern of middle-aged and elderly Chinese and to analyze the influence of selected variables on the use of dental services. A Guangdong Province population of 1573 35- to 44-year-olds and 1515 65- to 74-year-olds recruited from urban and rural communities was interviewed in their local dialect. It was found that 23% of the middle-aged and 24% of the elderly subjects had visited a dentist within the preceding year. The two most commonly cited reasons for not having seen a dentist for at least 3 years were: no perceived need, and no serious dental problems. Among subjects who had visited a dentist within 3 years, the 3 most commonly received treatments were: fillings, extractions, and dental prostheses. Furthermore, a logistic regression analysis showed that women, subjects who lived in urban areas, were better educated, were wealthier, and had better oral health knowledge were more likely to be a recent dental service user. In conclusion, dental service utilization among the adult Southern Chinese was found to be low, problem-driven, and influenced by some socio-economic factors.published_or_final_versio

Induced defense and its cost in two bryophyte species

Premise: Current knowledge about defense strategies in plants under herbivore pressure is predominantly based on vascular plants. Bryophytes are rarely consumed by herbivores since they have ample secondary metabolites. However, it is unknown whether bryophytes have induced defenses against herbivory and whether there is a trade-off between growth and defense in bryophytes. Methods: In an experiment with two peatland bryophytes, Sphagnum magellanicum Brid. and S. fuscum (Schimp.) H. Klinggr., two kinds of herbivory, clipping with scissors and grazing by mealworms (Tenebrio molitor L.) were simulated. At the end of the experiment, we measured growth traits, carbon-based defense compounds (total phenolics and cellulose) and storage compounds (total nonstructural carbohydrates) of these two Sphagnum species. Results: Grazing but not clipping increased total phenolics and C:N ratio and reduced biomass production and height increment. A negative relationship between biomass production and total phenolics was found in S. magellanicum but not in S. fuscum, indicating a growth–defense trade-off that is species-specific. Grazing reduced the sugar starch content of S. magellanicum and the sugar of S. fuscum. Either clipping or grazing had no effect on chlorophyll fluorescence (including actual and maximum photochemical efficiency of photosystem II) except that a significant effect of clipping on actual photochemical efficiency in S. fuscum was observed. Conclusions: Our results suggest that Sphagnum can have induced defense against herbivory and that this defense can come at a cost of growth. These findings advance our knowledge about induced defense in bryophytes, the earliest land plants

Characterization of implementation limits and identification of optimization strategies for sustainable water resource recovery through life cycle impact analysis

This is the final version. Available from Elsevier via the DOI in this record.How we manage alternative freshwater resources to close the gap between water supply and demand is pivotal to the future of the environment and human well-being. Increased scarcity of water for agricultural irrigation in semi-arid and arid regions has resulted in a growing interest in water reuse practices. However, insight into the life cycle impacts and potential trade-offs of these emerging practices are still limited by the paucity of systematic evaluations of different water reuse implementations. In this study, a host of environmental and human health impacts at three implementation levels of allowing water reclamation for crop irrigation was comparatively evaluated across the operational landscape via a combination of scenario modelling, life-cycle impact analyses and Monte Carlo simulations. Net harvesting of reclaimed water for irrigation was found to be dependent upon the sophistication of the treatment processes, since multistage and complex configurations can cause greater direct water consumption during processing. Further, the direct benefits of water resource recovery can be essentially offset by indirect adverse impacts, such as mineral depletion, global warming, ozone depletion, ecotoxicity, and human health risks, which are associated with increased usage of energy and chemicals for rigorous removal of contaminants, such as heavy metals and contaminants of emerging concern. Nonetheless, expanded simulations suggest the significance of concurrently implementing energy recovery, nutrient recycling, and/or nature-based, chemical-free water technologies to reduce the magnitude of negative impacts from engineered water reclamation processes.Royal Society (Charity)Beijing Talents FoundationBeijing Nova Program, ChinaNational Natural Science Foundation of ChinaYouth Innovation Promotion Association of the Chinese Academy of Science

An oral health survey in Southern China, 1997: Background and methodology

Relatively limited information is available about the oral health in the Guangdong Province of Southern China, the closest neighbor to Hong Kong. The study intended to explore the oral health status, knowledge, attitudes, and dental care utilization in the Guangdong population as a basis for formulating strategies for oral health prevention and treatment. Through multi-stage stratified and quota-sampling, individuals from urban as well as rural communities were selected (5- to 6-; 12-; 35- to 44-; and 65- to 74-year-olds; total N = 6251). Structured interviews and clinical examinations were performed. Inter-examiner reliability was high (K = 0.60-0.96). Samples of community water were taken for fluoride assessment. Overall, the sample surveyed was acceptably representative of the population, with some under-representation of rural residents and agricultural workers. Re-weighting was performed in appropriate analyses. The data analysis model used in the Second International Collaborative Study was used as a guide for the present data analysis. This approach has not previously been used on a Mainland Chinese population.published_or_final_versio

PTA and stenting in supra-aortic arch arteries

published_or_final_versio

An investigation of a quantum probability model for the constructive effect of affective evaluation

The idea that choices can have a constructive effect has received a great deal of empirical support. The act of choosing appears to influence subsequent preferences for the options available. Recent research has proposed a cognitive model based on quantum probability, which suggests that whether or not a participant provides an affective evaluation for a positively or negatively valenced stimulus can also be constructive and so e.g. influence the affective evaluation of a second oppositely valenced stimulus. However, there are some outstanding methodological questions in relation to this previous research. This paper reports the results of three experiments designed to resolve these questions. Experiment 1, using a binary response format, provides partial support for the interaction predicted by the quantum probability model and Experiment 2, which controls for the length of time participants have to respond, fully supports the quantum probability model. Finally, Experiment 3 sought to determine whether the key effect can generalize beyond affective judgements about visual stimuli. Using judgements about the trustworthiness of well-known people, the predictions of the quantum probability model were confirmed. Together these three experiments provide further support for the quantum probability model of the constructive effect of simple evaluations