Inhibition of the tempe mould, Rhizopus oligosporus, by ammonia

Abstract

The hyphal extension rate of Rhizopus oligosporus NRRL 2710 was slowed in the presence of 0·42 and 0·84 mmol NH3 l−1 and inhibited by 1·3 mmol l−1. Sporulation was prevented at NH3 concentrations of 0·42 mmol l−1 andabove. There was no evidence of toxicity due to NH+4 at concentrations up to 300 mmol l−1.Independent of the concentrations of NH3 or NH+4, the lower the pH value, in therange 6·0–9·0, the higher was the rate of hyphal extension. It is suggested that accumulationof toxic levels of NH3 could be responsible for the cessation of mould growth in tempe.

Tempe fermentation, innovation and functionality: update into the third millenium

“…Similarly, oxygen levels in tempe should remain higher than ca 0·4%; if the layer of beans is too thick, anaerobic conditions may prevail causing poor mycelium growth in the centre. Another limiting factor is the production of ammonia by degradation of nitrogenous compounds (Sparringa and Owens 1999b).…”

Effects of temperature, pH, water activity and CO2 concentration on growth of Rhizopus oligosporus NRRL 2710

“…Spore suspensions were prepared in purified water as previously described (Sparringa and Owens 1999). Rhizopus oligosporus spores do not swell or germinate in distilled water (Medwid and Grant 1984).…”

“…Rhizopus oligosporus NRRL 2710 is able to grow at pH values up to 9AE0 in the absence of ammonia (Sparringa and Owens 1999) but appears to be particularly sensitive to CO 2 at pH 7AE5, when growth is predicted to be inhibited by CO 2 concentrations > 15% (v/v) at a w 0AE96 and temperatures below $ 38°C (Fig. 6).…”

“…Studies on tempe moulds suggest that the most rapid growth occurs at pH values less than 6AE0 (Graham et al 1976;Sparringa and Owens 1999), temperatures around 40°C (Rathbun and Shuler 1983), O 2 concentrations above about 1% (v/v) and CO 2 concentrations of 1-10% (v/v) (Rathbun and Shuler 1983;de Reu et al 1995).…”

Changes in Macronutrient, Total Phenolic and Anti-Nutrient Contents during Preparation of Tempeh

“…Fat content was reduced during tempeh processing since lipase enzyme hydrolyses the triglyceride into free fatty acid [32]. It was also due to the microorganisms that use the fat as an energy source [33]. Table 1 showed that carbohydrate content in raw soya bean (3.63%) was significantly (p<0.05) highest compared to soaked (2.63%), cooked soya bean (2.64%) and tempeh (2.67%).…”