Factors influencing the free acidity of the fat ofPenicillium spinulosum in surface cultures

Studies are made of the effects of the following factors influencing the free acidity of the fat of P. spinulosum : (1) sterilisation of the felts in their metabolism solutions and when floated on distilled water; (2) the initial pH value of the medium; (3) addition of calcium carbonate to stabilise the pH of the medium at near neutrality during incubation; (4) the presence of glycerol as well as glucose in the medium; (5) addition of sodium sulphite. The results are discussed in relation to the metabolic processes of the mould.