New alternative method to measure fungal growth

What is it about?

In solid state fermentation (SSF), estimation of biomass presents difficulties as generally the fungal mycelium penetrates deep and remains attached with the solid substrate particles. Although many promising methods are available, the evaluation of microbial growth in SSF may sometimes become laborious, impractical and inaccurate. Essentially, this remains another critical issue for monitoring growth. In these studies, measurement of colour changes during SSF are presented as one of the potential techniques that can be used to describe growth, complementary to monitoring metabolic activity measurement, such as CER, OUR and heat evolution, which is directly related to growth. For the growth of Aspergillus awamori and Aspergillus oryzae on wheat bran, soybean hulls and rapeseed meal, it was confirmed that colour production was directly proportional to fungal growth. This colourimetric technique was also proved to be a feasible approach for fungal biomass estimation in SmF. This new approach is an important complementation to the existing techniques especially for basic studies. The key finding is that the colourimetric technique demonstrated and provided information of higher quality than that obtained by visual observation or spores counting.

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Why is it important?

Achieving a positive result in determining biomass remains a major challenge in SSF. Fungi are well characterised microorganisms and are widely used in solid state fermentation (SSF) due to their ability to colonise and penetrate into the solid substrate. The compressed structure of the mycelia and the solid substrate does not allow a complete recovery of the biomass, which may not be insurmountable. In contrast to submerged fermentation (SmF), SSF does not allow accurate biomass estimation. However, SmF faces the same problem when the fermentation media contain solid particles. Although significant advances have been made with the availability of various techniques; however, progress has been very unsatisfactory. In order for a particular strategy to be useful, it is necessary to have analytical methods for the analysis and evaluation of fungal growth. Such quantification is possible by measuring the colour produced in SSF and SmF using colourimetric technique. In this study, fungal fermentation of A. awamori and A. oryzae are carried out on complex heterogeneous solid media; wheat bran, soybean hull and rapeseed meal, which are constituted of various soluble and insoluble solid particles. This new approach is an important complementation to the existing techniques, especially for basic studies. The advantages of this method are its ease of use, fast, non-destructive, cheap, and requires no special and expensive reagents. The key finding is that the colorimetric technique demonstrated in this study provides good means to estimate growth than that obtained by visual observation or spores counting.

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