Changes in characteristic volatile aroma substances during fermentation and deodorization of Gracilaria lemaneiformis by lactic acid bacteria and yeast

Gracilaria lemaneiformis is a source of several bioactive natural products in China. Previously, we obtained Saccharomyces cerevisiae JJ4 and Lactobacillus paracasei paracasei RP38, that reduced the fishy odor of G. lemaneiformis. However, the associated deodorization mechanisms remain unclear. Here, G. lemaneiformis was fermented using single strain JJ4, single strain RP38, and both strains together. Dynamic changes in volatile aroma substances during fermentation were measured using HS-SPME-GC/MS. We found that the unpleasant aromas of raw G. lemaneiformis were primarily due to 3-octanone, cyclooctanol, and 1-methylcycloheptanol. Fermentation with lactic acid bacteria and yeast could reduce the substances associated with unpleasant aromas. The potentially characteristic aromatic substances consumed and produced by the different strains were determined using Opls-da and Spearman's correlations with VIP value >1 and |r| > 0.6. These results help to clarify the metabolic mechanisms by which different microbes reduce the fishy smell of G. lemaneiformis.