LAMP实时浊度法快速检测转基因玉米MON810

LAMP实时浊度法是采用环介导等温扩增（Loop Mediated Isothermal Amplification,LAMP）技术通过实时浊度仪实时检测反应过程中所产生的白色沉淀,从而实现对扩增全过程的监控,弥补了显色法只能观看反应终点的缺陷,使引物筛选和反应体系的优化有数据可依。本研究以转基因玉米MON810为研究对象,针对外源基因苏云金芽孢杆菌杀虫毒蛋白CryIA(b)与内源基因边界序列设计6条特异性引物,通过实时浊度法在63 ℃的恒温条件下完成检测,对检测的灵敏度、特异性、稳定性进行了评价。建立了转基因玉米MON810的LAMP实时浊度检测方法,该方法最低检出限为0.5%,与LAMP显色法和实时荧光PCR法进行结果比对,符合率为100%,经评价具有特异性高、稳定性强、准确简便等优点,非常适合转基因玉米MON810的快速检测,有较好的应用价值。     

Volatile organic compounds from the interaction between Fusarium verticillioides and maize kernels as a natural repellents of Sitophilus zeamais

Maize kernels are exposed to Sitophilus zeamais attack and Fusarium verticillioides infestation during storage, which can result in product deterioration and economic losses. The objective of this study was to evaluate the involvement of the Volatile Organic Compounds (VOCs) emitted by the fungi-corn system in grain-insect interactions. Volatiles emitted by healthy maize kernels were different from those emitted by fungal infected kernels, with the latter being enriched by alcohols, ketones and sesquiterpenes, which were considered early indicators of fungal contamination. The results demonstrated that the kernels exposed to the fungal VOCs and their pure compounds (1-octen-3-ol and 3-octanol) were less attractive and less damaged by S. zeamais than controls. In addition to compound adsorption, other processes may have caused the protective effect of exposed kernels against insect damage. This is the first contribution of the role of the fungal volatiles on the behavior of S. zeamais, and could provide an important contribution to the conservation of stored grains and pest management and an early indicator of fungal contamination.     

Sub-Saharan African Maize-Based Foods - Processing Practices,Challenges and Opportunities

ABSTRACT

In vast swathes of Sub-Saharan Africa, maize is the staple food with consumption of up to 450 g/person/day. Additionally, maize is used as a weaning food for infants as well as for special ceremonies, caring for the sick, aged and pregnant women. Malnutrition persists in regions with heavy maize consumption, partly due to compositional maize characteristics, nutrient loss during processing and consumer preferences. This paper reviews the traditional uses and processing of maize, opportunities and necessary improvements to ensure (micro)nutrient security. Better use of maize can enhance its contribution to meeting the dietary needs and livelihood of Africa’s growing populace.     

Evaluation of ability of ferulic acid to control growth and fumonisin production of Fusarium verticillioides and Fusarium proliferatum on maize based media

The aim of this study was to evaluate the efficacy of ferulic acid (1, 10, 20 and 25 mM) at different water activity (a_w) values (0.99, 0.98, 0.96 and 0.93) at 25 °C on growth and fumonisin production by Fusarium verticillioides and Fusarium proliferatum on maize based media. For both Fusarium species, the lag phase significantly decreased (p ≤ 0.001), and the growth rates increased (p ≤ 0.001) at the lowest ferulic acid concentration used (1 mM), regardless of the a_w. However, high doses of ferulic acid (10 to 25 mM) significantly reduced (p ≤ 0.001) the growth rate of both Fusarium species, regardless of the a_w. In general, growth rate inhibition increased as ferulic acid doses increased and as media a_w decreased. Fumonisin production profiles of both Fusarium species showed that low ferulic acid concentrations (1–10 mM) significantly increased (p ≤ 0.001) toxin production, regardless of the a_w. High doses of ferulic acid (20–25 mM) reduced fumonisin production, in comparison with the controls, by both Fusarium species but they were not statistically significant in most cases. The results show that the use of ferulic acid as a post-harvest strategy to reduce mycotoxin accumulation on maize needs to be discussed.     

Response of storage molds to different initial moisture contents of maize (corn) stored at 25 °C, and effect on respiration rate and nutrient composition

Maize was stored for 2 months in chambers maintained at 25 °C to simulate conditions observed in the central part of the “Corn Belt” of the United States when the grain warms because of high summertime temperatures after a period of winter storage. Maize was brought to three moisture contents (m.c.) within the range typically observed in farm and commercial storage, and was inoculated to simulate the amount of storage mold contamination typical of this situation. Certain of the experimental units were packed in insulation so that heat could accumulate within the grain masses to simulate hot spots. The wettest grain heated rapidly and became semi-anaerobic. The hot grain then dried rapidly, with the amount of moisture loss influenced by the ratio of water vapor pressures inside and outside the grain. The hot grain cooled and became more aerobic over time. New infections by storage molds, disappearance of viable field molds, development of kernel damage, and changes in atmospheric gases within the grain masses were correlated with the grain moisture or temperature and the rate at which the moisture and temperature changed. The rate of increase in new kernel damage was as high as 3.3% per week. Both the rate of respiration and the estimated ratio of starch to fat consumed were associated with the mean grain m.c. during the trial, and the estimated ratio of starch to fat consumed was in the range of 2.2/1–2.6/1 in the grain containing 16.6–18.2% m.c. That both fat and starch were consumed calls into question loss estimates based on starch metabolism alone. The fat content of the grain decreased more than 10% in some experimental units, but increased less than 5% in others. The protein content generally increased as other grain constituents were consumed.     

Significance of yeasts in the fermentation of maize for ogi production

Saccharomyces cerevisiae, Candida krusei, C. tropicalis, Geotrichum candidum, G. fermentans and Rhodotorula graminis were isolated during the fermentation of maize for ogi production. All the isolates except Geotrichum fermentans and Rhodotorula graminis were able to degrade phytate. All the yeasts strains exhibited lipase and esterase activities. Only S. cerevisiae (2.60%) and C. krusei (7.41%) exhibited amylase activities. Candida sp. produced wider zone of inhibition than the other yeasts strains tested during lipase activity while S. cerevisiae strains produced significantly wider zone of clearing as compared to the other yeasts for esterase activities. The study of inter-relationships between Lactobacillus plantarum and yeasts (C. krusei and S. cerevisiae) showed that the growth of the yeast strains were enhanced during fermentation by the presence of the lactic acid bacteria, but the growth of the L. plantarum strain was significantly enhanced especially by the C. krusei.     

The efficacy and persistence of diatomaceous earths admixed with commodity against four tropical stored product beetle pests

The efficacy and persistence of two commercially available enhanced diatomaceous earth (DE) products (Dryacide^® and Protect-It^®) against four common tropical storage pests (Prostephanus truncatus, Sitophilus zeamais, Callosobruchus maculatus and Acanthoscelides obtectus) were studied when admixed with typical host commodities at different application rates and relative humidities. Persistence of the enhanced DE treatments was considered after 3 and 6 months storage by assessment of both adult mortality and F1 progeny emergence. Both DEs usually increased parental mortality and reduced progeny emergence of all four insect species in comparison with the untreated control at both 50% and 60% r.h., and at all storage periods. However, efficacy was inversely related to duration of storage and over time the host commodity also became less suitable for insect development. Each insect species differed in its susceptibility to the DE treatments, highlighting the need for field application rates to be based upon the entire spectrum of pest species likely to be present during storage.     

Effect of different maize meal diets on growth and vitamin A: Case-study on chickens

South Africa embarked on mandatory vitamin and mineral fortification of wheat flour and maize meal in 2003 as part of a multi-faceted approach to alleviate malnutrition. However, it was reported, in 2008, that vitamin A deficiency increased despite the mandatory fortification programme. This motivates an investigation into the absorption of vitamin A as fortificant in the maize meal.