Synergetic effects of Lactobacillus plantarum and Rhizopus oryzae on physicochemical, nutritional and antioxidant properties of whole-grain oats (Avena sativa L.) during solid-state fermentation

Abstract

In this study, Lactobacillus plantarum strains, namely 70810, B1-6, and ZR were used to confirm the synergetic effects of co-inoculation with Lactobacillus and Rhizopus oryzae on whole-oat solid state fermentation (SSF). The results indicated that number of viable bacterial cells increased more quickly (10.72–11.23-fold higher) during co-inoculated SSF than that during pure Lactobacillus fermentation. Fungal ergosterol content reached slightly less during co-inoculation (137.04–155.12 mg/kg) than that during R. oryzae fermentation (193.64 mg/kg). However, compared to R. oryzae, R. oryzae combined with Lactobacillus produced more obvious hydrolysis of macromolecules and accelerated more water transformation from confined to free form. As for co-inoculated SSF of oat, the reducing sugar content reached the highest at 41.09–47.42 g/100g and then dropped, and free amino acid nitrogen content varied gradually until 40.66–41.67 mg/100g. Fermented oats (FOs) had higher total phenolic content than unfermented oat (UO) (2.56–2.72-fold, FO vs. UO), and their DPPH radical scavenging activity, ferric reducing capacity, and hydroxyl scavenging activity were increased 2.04-, 2.10-, and 1.99-fold at maximum (FO vs. UO), respectively. The Lactobacillus showed strain dependence during co-inoculated SSF, among which B1-6 displayed the best to enhance oat's overall quality.