Factors Affecting Yield and Safety of Protein Production from Cassava by Cephalosporium eichhorniae.

The properties of Cephalosporium eichhorniae 152 (ATCC 38255) affecting protein production from cassava carbohydrate, for use as an animal feed, were studied. This strain is a true thermophile, showing optimum growth at 45 degrees to 47 degrees C, maximum protein yield at 45 degrees C, and no growth at 25 degrees C. It has an optimum pH of about 3.8 and is obligately acidophilic, being unable to sustain growth at pH 6.0 and above in a liquid medium, or pH 7.0 and above on solid media. The optimum growth conditions of pH 3.8 and 45 degrees C were strongly inhibitive to potential contaminants. It rapidly hydrolyzed cassava starch. It did not utilize sucrose, but some (around 16%) of the small sucrose component of cassava was chemically hydrolyzed during the process. Growth with cassava meal (50 g/liter [circa 45 g/liter, glucose equivalent]) was complete in around 20 h, yielding around 22.5 g/liter (dry biomass), containing 41% crude protein (48 to 50% crude protein in the mycelium) and 31% true protein (7.0 g/liter). Resting and germinating spores (10 to 10 per animal) injected by various routes into normal and gamma-irradiated 6-week-old mice and 7-day-old chickens failed to initiate infections.

Sequential cold-sensitive mutations in Aspergillus fumigatus. II. Analysis by the parasexual cycle.

From Aspergillus fumigatus I-21 (ATCC 32722), which grows at temperatures from 12 to 50 degrees C, three multistep, independently derived, cold-sensitive mutants unable to grow at 37 degrees C or below (Cs-37) were obtained by sequential exposure to ethylmethane sulfonate (strain AT2) or N-methyl-N'-nitro-N-nitrosoguanidine (AT1 and AT3). These mutants and ON5, a five-step Cs-37 mutant, were marked by mutations affecting spore color and nutritional requirements and crossed in four combinations by classical parasexual means. The heterokaryons demonstrated partial complementation with respect to auxotrophic requirements (suboptimal growth on minimal medium) and cold sensitivity (growth at 37 degrees C but not at 25 degrees C). Most presumed diploids, formed by exposure of the heterokaryons to d-camphor vapors, showed complete complementation but were unstable, as demonstrated by variations in spore sizes and markedly different ratios of segregant classes derived from different clones. Analysis of the segregants of the diploids or aneuploids, induced by Benomyl, indicated that multiple genes were responsible for cold sensitivity in each Cs-37 mutant, since segregants with various levels of cold sensitivity were obtained. The higher than predicted frequency of reversion to temperatures two or more steps back in the sequence of cold sensitivity mutations suggested that these genes or their products interacted. No Cs-37 segregant yielding a consistently lower frequency of revertants than the original mutants was obtained.