An enzyme-linked immunosorbent assay for monitoring of Aspergillus ochraceus growth in coffee powder, chilli powder and poultry feed.

AIMS: The work was carried out to develop an immunoassay for estimation of Aspergillus ochraceus biomass on solid substrate. METHODS AND RESULTS: An indirect noncompetitive enzyme-linked immunosorbent assay (ELISA) was developed for determination of fungal biomass in food commodities using antibody raised against A. ochraceus mycelial antigen. The sensitivity of the assay was linear in the range of 10-160 microg fungal biomass per millilitre extract of coffee (R(2)=0.989), poultry feed (R(2)=0.987) and chilli (R(2)=0.989). The growth of A. ochraceus in the food commodities like chilli, coffee beans and poultry feed, under the influence of two levels of moisture (20% and 30%) were monitored by the ELISA. The maximum fungal colonization was observed in poultry feed (9.8 and 11.8 mg g(-1)) followed by coffee beans (6.8 and 11.3 mg g(-1)) and chilli (5.1 and 6.3 mg g(-1)) at 20% and 30% moisture after 20 days of incubation. Similarly the fungus produced maximum ochratoxin A in poultry feed (25 and 120 microg g(-1)) followed by coffee beans (8 and 24 microg g(-1)) and chilli (0.2 and 0.45 microg g(-1)) at 20% and 30% moisture after 20 days of incubation. CONCLUSIONS: The method can be used for quantitative estimation of fungal biomass and comparison of fungal colonization in food substrates varying in composition. SIGNIFICANCE AND IMPACT OF THE STUDY: The method can be adapted for studying the fungal colonization in different solid substrates under different culture condition. The method is sensitive to mould colonization of >or=0.02% (w/w) and can be used for early detection of specific fungal infestation in food commodities.

PCR-restriction fragment length analysis of aflR gene for differentiation and detection of Aspergillus flavus and Aspergillus parasiticus in maize.

Contamination of food and feedstuffs by Aspergillus species and their toxic metabolites is a serious problem as they have adverse effects on human and animal health. Hence, food contamination monitoring is an important activity, which gives information on the level and type of contamination. A PCR-based method of detection of Aspergillus species was developed in spiked samples of sterile maize flour. Gene-specific primers were designed to target aflR gene, and restriction fragment length polymorphism (RFLP) of the PCR product was done to differentiate Aspergillus flavus and Aspergillus parasiticus. Sterile maize flour was inoculated separately with A. flavus and A. parasiticus, each at several spore concentrations. Positive results were obtained only after 12-h incubation in enriched media, with extracts of maize inoculated with A. flavus (101 spores/g) and A. parasiticus (104 spores/g). PCR products were subjected to restriction endonuclease (HincII and PvuII) analysis to look for RFLPs. PCR-RFLP patterns obtained with these two enzymes showed enough differences to distinguish A. flavus and A. parasiticus. This approach of differentiating these two species would be simpler, less costly and quicker than conventional sequencing of PCR products.

Nutritional quality of lactic fermented bitter gourd and fenugreek leaves.

Pediococcus pentosaceus was selected from isolates obtained from the naturally fermenting bitter gourd and fenugreek leaves based on its high titre and broad spectrum of inhibitory activity against spoilage organisms. This strain was then employed for fermentation of bitter gourd and fenugreek which resulted in a more acceptable product having enhanced fat, pyridoxine and ascorbic acid levels. It was of interest to note that vitamin B12 was formed in the fenugreek as a result of the fermentation.

Effect of long term feeding and withdrawal of aflatoxin B1 and ochratoxin A on kidney cell transformation in albino rats.

Subacute doses (1/20 LD50) of aflatoxin B1 and ochratoxin A were fed to weanling albino rats individually and in combination for 36 weeks and then rats were maintained on toxin free normal diet for a period of 24 weeks. Livers of rats were fatty, wherever aflatoxin was administered but the enzyme activity did not show significant differences among various groups. However, in a few individuals whose livers were severely affected, higher concentrations of urine creatinine, liver RNA and DNA, and ALT enzyme activity were recorded. Histopathological examination showed various stages of hepatoma and hepatocarcinoma including nodular hyperplasia, hypertrophy, vacuolisation, degeneration, pseudolobulation, cellular infiltration and fibrosis of liver of rats fed with aflatoxin individually and in combination. Few anaplastic cells in the corticomedullary region and nuclear enlargement of proximal tubular epithelium of kidney were found wherever combined toxin and ochratoxin alone were administered. Liver tumor expression was time dependent.

Behaviour of Aspergillus flavus in presence of Aspergillus niger during biosynthesis of aflatoxin B.

Aspergillus niger or Aspergillus tamarii when grown as mixed cultures with toxigenic A. flavus inhibits biosynthesis of aflatoxin by A. flavus, owing primarily to its ability to produce inhibitors of aflatoxin biosynthesis and to their ability to degrade aflatoxin. Gluconic acid partly prevents aflatoxin production. The other factors such as changes in pH of the medium and the effect on the growth of a. flavus have no role in imparting capabilities to these cultures to inhibit aflatoxin production by A. flavus.