Quantification of Lentinus squarrosulus in fermentation processes using qPCR

Abstract Fungi are increasingly being used to make effective use of by-products from the food industry. Fungal fermentation can convert by-products into a protein-rich food ingredient suitable for human consumption, for example in meat alternatives. However, accurately quantifying the fungal content of the fermentate remains challenging due to the presence of substrate residues. This study developed a qPCR method to quantify the mycelium of the basidiomycete Lentinus squarrosulus cultivated in media containing the by-products beet pulp and molasses. Species-specific primers targeting the ITS region were designed. Optimized qPCR conditions enabled rapid and reproducible quantification of the fungal content within a range of 10–60%. The fungal content calculated using this method for a growth curve of L. squarrosulus in beet pulp-molasses medium was compared with the results of quantification using the biomarkers chitin and ergosterol. Comparable results were achieved for the culture days 3, 5 and 7, with no significant differences observed.