The ability of Humicola insolens COONEY & EMERSON and Aspergillus fumigatus FRES. t o cause biochemical changes in the components of milled Sorghum guineense grains and the factors necessary for these activities were studied. Significant losses (at p = < 0.01) in the cellulose, hemicellulose, diastase and ethanol soluble fractions of the malted grains were recorded on inoculation with asexual spores of A . fumigatus and H . insolens and 21 days of incubation a t 35 "C and 45 "C, respectively. This was accompanied by a corresponding rise in the total nitrogen components of the medium with period of incubation. None of the microbes was able to degrade the lignin components of the malted grains. While A . fumigatus was most active on the grains a t 35 "C and p H 6.2, EI. insolens grew best at 45 "C and p H 5.4.
When both fungi were grown on varying sources of carbon and nitrogen good results were obtained on most of them with optimal growth recorded on starch and dextrin and the organic nitrogen sources L-asparagine, L-glutamic acid and L-alanine. Both fungi also produced extracelluearly amylase, cellulases, pectate Iyase, xylanase, protease, lipase, DNase and RNase. The potential health risks which the presence of these fungi on malted Sorghum grains pose to the consumers of the end products are discussed.
Sorghum g u i n e e n s e STAPF is native to
West Africa and high yielding varieties are commercially cultivated in the savannah grassland areas of northern Nigeria. The airdried grains are fed to cattle and sheep while the malted grains are used in the brewing of various alcoholic beverages (EKUNDAYO 1969, PAPARUSI et al. 1973). The malting of Sorghum grains in Nigeria involves raising the moisture levels from 1 0 . 0 -1 2 ~o by a process of steeping interspersed with periods of air rests. The germination process is usually carried out a t room temperature which is in the range 28"-30 "C in the humid south of Nigeria after which the grains are air-dried and stored. The malting conditions are particularly suitable for mould infestation of the grains leading to spoilage and reduction in market value. Several mould species were obtained by EKUNDAYO (1969) and FAPARUSI et al. (1973), some of which are known to produce potent mycotoxins.
This report deals with the degradation of malting Ayorghum grains by such saprnphytic fungi and the conditions necessary for their growth.