Effects of two kinds of Bacillus on flavour formation of Baijiu solid-state fermentation with pure mixed bacteria

Bacillus plays a unique role in Baijiu brewing, but its functions have not been fully explored. In this study, Aspergillus niger, Saccharomyces cerevisiae and Thermoactinospora rubra were used as chassis microorganisms in a fermentation system. Bacillus subtilis and Bacillus licheniformis, which are common in Maotai-flavoured Baijiu, were studied in the fermentation. Their metabolic differences and effects on the formation of Baijiu flavour in the process of stacking fermentation were analysed. The combined fermentation system of B. licheniformis showed the highest glucose metabolism, good flavour production, the greatest number of flavour compounds and the highest contents of important compounds, including ethanol (80.51%) and tetramethylpyrazine (0.35%). The maximum concentrations of glucan, maltotriose, maltose monohydrate and glucose were 349.64, 70.98, 64.34 and 51.31 mg g(-1), respectively. These results suggested that the metabolism of sugar and its derivatives was closely related to the overall flavour of the fermentation system.