Abstract
The main objective of this study was to evaluate the growth rate of Lactobacillus ssp. and Streptococcus thermophilus in 6 types of plant water extract (Lycium barbarum, Illicium verum, Psidium guajava, Curcuma longa, Allium sativum, and Codonopsis pilosula) with two different concentration (10% and 2.5%; w/v) both in the presence and absence of fish collagen as a protein source during incubation at 37 degrees C. The growth rate was measured using a spectrophotometer, and the absorbance was taken every 4 hours for 28 hours (S. thermophilus) and 48 hours (Lactobacillus spp.). The effects of plant water extract on bacterial growth were dose-dependent. The growth of S. thermophilus and Lactobacillus spp. in all samples increased with incubation time. After about 12 hours for S. thermophilus in 2.5% plant extract and 16 hours for other samples with or without fish collagen, it began to plateau. The growth rate of Lactobacillus spp. was significantly higher (p<0.05) than S. thermophilus. Illicium verum and Lycium barbarum, both in the presence and absence of fish collagen, showed the most significant influence of bacterial growth among other samples. Fish collagen had a slight effect on bacteria growth during the incubation period. In conclusion, all plant samples could be an effective vehicle for carrying Lactobacillus ssp. and S. thermophilus.