C. W. Hesseltine

Microbiological studies on amylolytic oriental fermentation starters

Ragi and ragi-like starters were obtained from China, India, Indonesia (Java and Bali), Malaysia, Nepal, Philippines, and Taiwan. These starters have a number of names in each country (murcha, bubod, Chinese yeast). The microorganisms found in 41 samples examined were 3 genera of the Mucorales (Rhizopus, Mucor, Amylomyces), yeasts and bacteria. Except for a few chance contaminants only Mucoraceous fungi were found, and the appearance and growth of colonies of yeasts and bacteria indicate that only 2 or 3 species of each were present. The starters from different countries sold under different names are identical in their flora except that Amylomyces was rarely, if ever, a part of the murcha flora in samples from Nepal. The range in counts were 4x103 to 2.1×108 bacteria, 4×103 to 6.1×108 for molds and yeasts, and 3×103 to 6.1×108 for yeasts alone. The anaerobic count ranged from 3×102 to 1.5×108 and was made up of both yeasts and bacteria. Every sample contained yeast and at least one Mucoraceous mold. Amylomyces was shown to survive long periods of time — as many as 5 years at room temperature resulted in retained amylolytic activity. There was a considerable reduction in isolates of Mucor and Rhizopus with long periods of storage. Chlamydospore germination was seen for the first time in Amylomyces.

• %Biochemical Modification of Fats by Microorganisms: A Preliminary Survey

Over 100 different strains of bacteria, actinomycetes, fungi and yeasts were incubated at 28 C for five days in the presence of soybean oil. Some soybean oil was consumed by many microorganisms, and some was also hydrolyzed to free fatty acids.Aspergillus oryzae, two different strains ofAmylomyces rouxii andRhizopus oligosporus hydrolyzed the oil completely (95%). The fatty acids fromAspergillus flavus fermentation contained less linolenic acid than the original soybean oil. Lipase was found intra- and extracellularly when microorganisms were grown in the presence of soybean oil.

Mold development in ears of corn from tasseling to harvest.

Reports in the literature indicate that corn at the time of harvest typically is infected (55-92% of the kernels) with a variety of fungi. This study was initiated to determine the time, kind, and progressions of natural fungal infection of corn in the field. During the 1974 growing season, a central Illinois cornfield was sampled weekly (15 wk) from the emergence of silks until harvest. VVeather data were recorded. At each sampling, 10 ears were hand picked and brought into the laboratory, where silks, and kernels from tip, middle, and butt of each ear were aseptically removed and plated on yeast e..;::tract agar containing tetracycline. After incubation at 28 C for 4-7 da, the fungi growing from the silks and kernels were identified. Fusaria were identified the third week and had a peak occurrence in the eighth week. Yeasts followed the same trend. Overall, Fusaria were by far the most abundant molds infecting the corn kernels. A cremollimn strictum was identified the sixth week, whereas Nigrospora sp. was not observed until the eighth week. Both progressively increased to harvest. Species of Alternaria and Penicillium were sporadic and found at low levels. No Aspergillus species were encountered. Generally, maturing corn was relatively free of fungal contamination until the late dent stage.

Aflatoxin and Mold Flora in North Carolina in 1977 Corn Crop

In a 1977 survey, 187 of 238 maize samples from the Piedmont and Coastal Plain area contained aflatoxin; of these 139 were above the 20 p.p.b. guideline. Aflatoxin G1 was found in 32 samples from the Piedmont/mountain area. The highest level of aflatoxin found was 3622 p.p.b. In general, the higher the percentage of insect-damaged maize the higher the aflatoxin levels found. The sample with the most insect damaged maize (11%) showed a level of 2208 p.p.b., and all samples with 4.5% or more insect damage contained aflatoxin. In general, the greater the infection of maize by Aspergillus flavus the higher the level of aflatoxin, with 7 samples having 40-44 undamaged kernels out of 50 infected. A. niger was found in 10.9% of the samples, but there was no positive correlation with the amounts of aflatoxin found. Strs. of Penicillium funiculosum series isolated from S. Carol. were found again in 25.3% of the total kernels examined. Few other P. or A. spp. were seen. Maize germination was high in most samples. Assuming that most of the aflatoxin G1 was produced by A. parasiticus, a definite ecological correlation was found between G1 and a specific area, i.e. the Piedmont/mountain area.

The Genus Absidia: Gongronella and Cylindrical-Spored Species of Absidia

SUMMARYThe synonymy of the genus Absidia is discussed, and a new subgenus Mycocladus is proposed to include all species of Absidia which have suspensors without long finger like projections surroun...

Effect of temperature on production of aflatoxin on rice by Aspergillus flavus

The effect of temperature on formation of aflatoxin on solid substrate (rice) byAspergillus flavus NRRL 2999 has been studied in some detail. The optimum temperature for production of both aflatoxin B1 and G1 under the conditions employed is 28° C. Comparable yields of B1 were obtained at 32° C, but considerably less G1 was produced at this temperature. Both B1 and G1 were found in lesser amounts at temperatures above 32° C, and the aflatoxin content of rice incubated at 37° C was low (300–700 ppb) even though growth was good. Reducing the temperature from 28° to 15° C resulted in progressively less aflatoxin, but 100 ppb of B1 was detected in cultures incubated 3 weeks at 11° C. No aflatoxin was produced at 8° C. The ratio of the four aflatoxins is affected by temperature. At the lower temperatures, essentially equal amounts of aflatoxin B1 and G1 were produced, whereas at 28° C, approximately four times as much B1 was detected as G1. At the higher temperatures, relatively less G was formed, until at 37° C, less than 10 ppb was detected.

Utilization of zearalenone-contaminated corn for ethanol production.

Two lots of yellow corn, severely damaged byFusarium fungi and contaminated with 8.0 and 33.5 ppm zearalenone, respectively, were used for ethanol fermentations. Substrate corn (5-kg samples) was processed in a laboratory procedure similar to that used by the fermentation industry. Stillages obtained were 7.0 to 9.0% ethanol. Ethanol was recovered by distillation, residual grain solids by filtration, and solubles by concentration. No zearalenone could be detected in the ethanol fraction. Zearalenone in the original corn was concentrated in the residual solids and solubles, which are generally used for animal feed. Treatment with formaldehyde significantly reduced the level of zearalenone in fermentation solids. Ammonium hydroxide was a much less effective agent for toxin degradation.

Antibacterial activity produced by molds commonly used in oriental food fermentations.

(1972). Antibacterial Activity Produced by Molds Commonly used in Oriental Food Fermentations. Mycologia: Vol. 64, No. 1, pp. 218-221.

Aflatoxin Occurrence in 1973 Corn at Harvest. II. Mycological Studies

SUMMARY Since aflatoxin is formed in corn in the field before harvest, our objectives were to determine at harvest (a) the amount of Aspergillus flavusinfected corn kernels, (b) the amount of A. flavus spores on the surface of corn, (c) the total amount of fungus-infected kernels, (d) the occurrence of A flavus spores in and on insects from corn reported in the first paper of this series, and (e) the correlation between A. flavus infection and occurrence of aflatoxin. The corn was collected at harvest from seven counties in northeastern South Carolina and dried to less than 13% moisture as quickly as possible. Of the 152 aflatoxin-positive samples, 120 showed one or more kernels internally infected with A. flavus and of the 145 aflatoxin-negative samples, 59 showed infection. Of the 297 samples examined, 276 had one or more kernels with surface contamination of A. flavus spores, and in 75 of the samples every kernel was contaminated. When kernels were surface disinfected, 224 samples (50 kernels each) showed 100% internal mold contamination. One or more kernels of 185 samples were infected with A. flavus; this number represents 60% of the total samples. Of the 375 insects collected and examined for A. flavus from the corn samples, 247 showed A. flavus present. Of the 85 rice weevils, 78 were carrying A. flavus spores and of the other 290 insects, 165 were contaminated. Besides A. flavus, the predominant infecting fungi internally were two species of Penicillium and Fusarium. Members of the Mucorales were rarely seen. The occurrence of Aspergillus flavus Link ex Fries and A. parasiticus Speare growing on corn plants in the field before harvest has rarely been recorded (Taubenhaus, 1920). From 0.02 to 0.09% infection of corn kernels before harvest was reported by Tuite (1961) from Indiana. The highest single instance had a 22% infection by A. flavus. In 1970, Tuite and Caldwell (1971) found an average incidence of 0.4% kernel infection before harvest in corn also in Indiana. The A. flavus incidence in southern Indiana counties was 1.2% as compared to 0.2% in northern counties. Rambo et al. (1974) reported a 0.03 to 0.08% incidence of

Carbon and nitrogen utilization by Rhizopus oligosporus.

SUMMARYThe utilization of various carbon and nitrogen compounds by Rhizopus oligosporus Saito NRRL 2710 was investigated. The principal components of the soluble carbohydrates of soybeans, i.e., st...