Characterization of the growth properties of garlic endophytes and their roles in the formation of black garlic

Abstract This study aimed to characterize the growth properties of the four dominant endophytes from garlic and explore their effects on the black garlic fermentation. Four bacteria showed a certain heat resistance (more than 7 Lg CFU/mL of vegetative cells at 50 °C) and a wide pH growth range of 5–9. The allicin and 5-HMF in black garlic caused their limited decreases (7.45%–69.73% for allicin and 17.78%–30.68% for 5-HMF). Four strains were also found to have 7.70–31.91 U/mL of neutral protease, 3.32–16.72 U/mL of alkaline protease and 0.65–0.81 U/mL inulinase activities. Furthermore, the browning degree of black garlic increased by 0.81%–2.78% due to the inoculation of B. methylotrophicus, B. amyloliquefaciens and B. subtilis, while B. licheniformis slowed down the processing. Further analysis showed that a 27.70%–99.47% increase in the reducing sugar content was closely associated with the higher browning samples. Multivariate analysis revealed that the black garlic at different processing times were clearly distinguished from one another, but the differences caused by different strains were limited. The results first confirmed that the microbial strains were involved in the fermentation of black garlic at low temperatures by mainly affecting the levels of monosaccharides.