Colour changes as an indicator for estimating fungal growth in solid state fermentation

ABSTRACT

@#Aims:In this study, measurement of colour changes during solid state fermentation (SSF) are presented as one of the potential techniques that can be used to describe growth, complementary to other biomass estimation, such as weight of fungus, spores concentration, organic matter loss, glucosamine and enzyme activity, which is directly related to growth.Methodology and results: In this study, fungal fermentation of Aspergillus awamoriand A.oryzaeare carried out on complex heterogeneous solid media; wheat bran, soybean hull and rapeseed meal, which are constituted of various soluble and insoluble solid particles. Fermented mass was extracted using distilled water to obtain a cell free extract, which canbe determined quickly and accurately using UV-Visible spectrophotometermeasured absorbance at 300 nm. The results showed a significant correlation between colours produced from fungal SSF and the concentration of spores, weight of fungus cells, organic matter loss, glucosamine and enzyme activity. We found that the colour density proportionally increased when the studied parameters mentioned above increased.For the growth of A. awamoriand A. oryzaeon wheat bran, soybean hulls and rapeseed meal, it was confirmed that colour production was directly proportional to fungal growth. In general, colour-based methods seem to be the most promising approach for biomass estimation in SSF.Conclusions, significance and impacts of studyThe theory of measuring colour changes in SSF by UV-visible spectroscopy demonstrates that the colour method gives some valuableinformation than just obtaining a visual observation or spore count to describe growth of fungal mycelium in SSF. The ideas obtained from this exercise might provide a quick and convenient method for quality control of fungal growth. The advantages of this method are that the procedure is simple to carry out, it is non-destructive and no special and expensive reagents are required and the process is very cheap.This newapproach is an important complimentation to the existing techniques especially for basic studies.