A mycotoxicological survey on soil-borne Aspergilli in 268 soil samples collected from 11 areas in Shantung, China, was carried out. Aspergilli were isolated by using the soil-plate method on Czapek's agar, incubating the plates at 37°C for 10 days. The most common Aspergilli were Aspergillus flavus, A. fumigatus, A. niger, A. terreus and Emericella nidulans. Petromyces alliaceus was also frequently isolated. A higher occurrence of A. flavus was generally shown in the soil samples of road side and cultivated fields; while Emericella spp. highly occurred in those from paddy field, road side and cultivated fields. The Emericella isolates were identified with E. acristata and E. nidulans. For the 45 isolates of A. flavus and A. parasiticus, their ability to produce afiatoxins (AF) was examined on YES medium at 25°C for 7 days. The following AFB1 producers were found by TLC : A. flavus (12 positive strains/44 tested strains) and A. parasiticus (1/1). The levels of AFB1 production ranged between trace and 32μg per ml. For the 44 isolates of E. acristata and E. nidulans, their ability to produce sterigmatocystin (STG) was examined on rice at 25°C for 21 days. The following STG producers were found by HPLC: E. nidulans (26/43). The levels of STG production ranged between 0.26 and 5.63 μg per g of the rice.
Iturin A, antifungal lipopeptide reported by Peypoux and Isogai, was isolated from submerged culture of Bacillus subtilis NK 330 and its growth inhibitory activity toward aflatoxigenic fungus A. parasiticus NRRL 2999 was investigated. At 50 ppm of iturin A in the medium, the toxin production was completely inhibited while the growth of A. parasiticus was partially restricted. In contrast, the same amount of cycloheximide showed no significant influence on the toxin production by this fungus.
Chaetochromin A has been studied in detail with regard to the swelling-inducing effect on mitochondria in vitro to gain insight into the interrelationship between its respiration-impairing and swelling-inducing activities. Chaetochromin A elicited very rapid swelling of mitochondria in isotonic CsCl, RbCl, KCl, NaCl, and LiCl solutions, showing eminent differences in the magnitude and rate of swelling. The swelling amplitude was prominently larger in the KCl medium than those in the other kind of alkali metal chloride media, showing a distinct cation selectivity in the order of K+>>Cs+, Na+, Rb+>>Li+, and a sharp predominant K+-selectivity was observed in the initial rate of swelling. Chaetochromin A was tested for the induction of swelling in the isotonic KCl medium at various pH between pH 5 and 9. The amplitude and velocity of swelling were markedly increased corresponding to the decrease of the pH in the test system. A pH optimum for the swelling induction seemed to locate at much lower pH than the physiological pH range.
The effect of methanol and ethanol to control Aspergillus flavus infection and aflatoxin (AF) contamination in high moisture maize kernels was studied. When treated with 3% of pure methanol (v/w) to maize kernels in traditional jute bags three days after shelling and then stored for 10 days, infected kernels by A. flavus and AF accumulation were 56% and 36 ppb respectively, while those of untreated maize were 96% and 248 ppb. When either 3% (v/w) of pure methanol or ethanol was treated to maize kernels immediately after shelling, ten days later, alcohol-treated maize showed low percentage of A. flavus infection (1 or 1.5%) and aflatoxin accumulation (<5 or 13 ppb), while untreated maize was high frequency of A. flavus infection (65%) and high level of AF accumulation (180 ppb).