Exopolysaccharide-Producing Lacticaseibacillus rhamnosus Space Mutant Improves the Techno-Functional Characteristics of Fermented Cow and Goat Milks

Lacticaseibacillusrhamnosus Probio-M9(Probio-M9) is increasingly used as a co-fermentation culture in fermentedmilk production. Recently, a capsular polysaccharide (CPS)- and exopolysaccharide(EPS)-producing mutant of Probio-M9, HG-R7970-3, was generated byspace mutagenesis. This study compared the performance of cow andgoat milk fermentation between the non-CPS/-EPS-producing parentalstrain (Probio-M9) and the CPS/EPS producer (HG-R7970-3), and thestability of products fermented by the two bacteria. Our results showedthat using HG-R7970-3 as the fermentative culture could improve theprobiotic viable counts, physico-chemical, texture, and rheologicalproperties in both cow and goat milk fermentation. Substantial differenceswere also observed in the metabolomics profiles between fermentedcow and goat milks produced by the two bacteria. Comparing with Probio-M9-fermentedcow and goat milks, those fermented by HG-R7970-3 were enriched ina number of flavor compounds and potential functional components,particularly acids, esters, peptides, and intermediate metabolites.Moreover, HG-R7970-3 could improve the post-fermentation flavor retentioncapacity. These new and added features are of potential to improvethe techno-functional qualities of conventional fermented milks producedby Probio-M9, and these differences are likely imparted by the acquiredCPS-/EPS-producing ability of the mutant. It merits further investigationinto the sensory quality and in vivo function of HG-R7970-3-fermentedmilks.