The effect of germination on the level of phytase activity and the contents of phytates and phosphorus of five Nigeria grown cereal grains was studied. The cereals screened were rice (Oryza sativa), maize (Zea mays), millet (Panicum miliaceum), sorghum (Sorghum bicolor) and wheat (Triticum aestivum). Phytase activity was high (0.21-0.67 U g -1 ) in all samples. Phytate content ranged between 5.6 and 6.2 mg g -1 while total phosphorus content ranged between 3.3 and 4.3 mg g -1 . During germination, the level of phytase activity increased and reached its maximal value after seven (16-fold), six (5-fold), five (7-fold), seven (3-fold) and eight (6-fold) days of germination for rice, maize, millet, sorghum and wheat respectively. After this initial increase, phytase activity declined slightly (P<0.05). The increase in phytase activity during germination was accompanied by a significant reduction in phytate (P<0.05) and a small but significant increase in total phosphorus.

Tropical African yambean (Sphenostylis stenocarpa L) is an under-utilised hardy, protein-rich legume. Antinutrients and the excessively long cooking time (4-6 h), among other factors, limit the food use of African yambean seeds. To reduce these limitations, non-traditional, less energy-consuming processing methods are required. Seeds of different varieties were (i) examined for ingredients and (ii) fermented with Lactobacillus plantarum. Comparisons with traditionally cooked beans were made. Protein content and in vitro protein digestibility were increased slightly by fermentation or cooking. Reductions in trypsin and α-amylase inhibitor activity and tannin ranged from significant to complete. The contents of potentially very toxic cyanogenic glycosides and flatulence-causing α-galactosides were high in raw beans. Reduction by fermentation (by 85%) was clearly more effective than by traditional cooking (10-20%). The results demonstrate (i) that fermentation can substantially improve the nutritional quality and (ii) that the energy requirement to produce a basic consumable fermented food from African yambean is only 10% of that of traditional cooking. On these grounds, widespread application of lactic acid fermentation by individuals or small-scale industries would be advantageous in the context of small-household economy, environmental protection, health and long-term sustainable agriculture in Nigeria.

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The fungus commonly used in tempeh production, Rhizopus oligosporus (DSMZ 1964), was grown in rice flour suspension and two intracellular phytases (RO1 and RO2) were isolated from the fungus, purified to near homogeneity in a five-step process and characterized. Enzyme recoveries after purification were 1.3% (RO1) and 1.6% (RO2) in relation to the phytase activity in the crude extract. Their estimated molecular mass was 45.0 Ϯ 5.0 kDa. The purified proteins belong to the acid phytases and they both exhibit two distinct pH optima at 3.0 and 4.5 for RO1 and 3.0 and 5.0 for RO2. Optimal temperature for the degradation of sodium phytate was determined to be 60C for RO1 and 55C for RO2. Kinetic parameters for the hydrolysis of sodium phytate were K m = 1.6 mM (RO1) and 0.13 mM (RO2) and V max = 0.044 U for RO1 and 0.155 U for RO2. The phytases from R. oligosporus exhibit a broad affinity for various phosphorylated compounds. PRACTICAL APPLICATIONSThis work reports the isolation, purification and characterization of two intracellular phytases from the tempeh fungus Rhizopus oligosporus. Interest 4 Corresponding in these enzymes has been stimulated by the fact that phytase supplements increase the availability of phosphorus in pig and poultry feed, and thereby reduce environmental pollution due to excess phosphate excretion in areas where there is intensive livestock production. One of the purified phytase fractions RO2 showed promising enzymatic properties such as low K m for phytate. This could be exploited for further biotechnological applications especially in the feed industry.

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