RESUMO
This study aimed to evaluate the effect of Lactobacillus plantarum 200655 and fructooligosaccharides (FOS) on soymilk fermentation and the neuroprotective effects of fermented soymilk (FS). The addition of FOS did not affect the physicochemical properties during fermentation. It helped that L. plantarum 200655 survive for 21 days of storage at 4 °C. FOS increased the ß-glucosidase activity of L. plantarum 200655, total phenolic content, and antioxidant activities, such as radical scavenging and reducing power of FS. In addition, FS with FOS exerted neuroprotective effects in SH-SY5Y cells against H2O2-induced oxidative stress. FS with 3% and 5% FOS (FS3 and FS5) significantly increased cell viability and gene expression of neuronal markers, such as brain-derived neurotrophic factor and tyrosine hydroxylase. Moreover, FS3 and FS5 significantly reduced lactate dehydrogenase release and the gene expression of Bax/Bcl-2 ratio, caspase-9, and caspase-3. These results indicated that FS3 and FS5, with enhanced antioxidant properties, could protect SH-SY5Y cells against H2O2-induced damage. Therefore, soymilk fermented with L. plantarum 200655 and FOS can be used as a prophylactic functional food with neuroprotective effects against oxidative stress.
RESUMO
This study aimed to optimize medium composition and culture conditions for enhancing the biomass of Lactobacillus plantarum 200655 using statistical methods. The one-factor-at-a-time (OFAT) method was used to screen the six carbon sources (glucose, sucrose, maltose, fructose, lactose, and galactose) and six nitrogen sources (peptone, tryptone, soytone, yeast extract, beef extract, and malt extract). Based on the OFAT results, six factors were selected for the Plackett- Burman design (PBD) to evaluate whether the variables had significant effects on the biomass. Maltose, yeast extract, and soytone were assessed as critical factors and therefore applied to response surface methodology (RSM). The optimal medium composition by RSM was composed of 31.29 g/l maltose, 30.27 g/l yeast extract, 39.43 g/l soytone, 5 g/l sodium acetate, 2 g/l K2HPO4, 1 g/l Tween 80, 0.1 g/l MgSO4·7H2O, and 0.05 g/l MnSO4·H2O, and the maximum biomass was predicted to be 3.951 g/l. Under the optimized medium, the biomass of L. plantarum 200655 was 3.845 g/l, which was similar to the predicted value and 1.58-fold higher than that of the unoptimized medium (2.429 g/l). Furthermore, the biomass increased to 4.505 g/l under optimized cultivation conditions. For lab-scale bioreactor validation, batch fermentation was conducted with a 5-L bioreactor containing 3.5 L of optimized medium. As a result, the highest yield of biomass (5.866 g/l) was obtained after 18 h of incubation at 30°C, pH 6.5, and 200 rpm. In conclusion, mass production by L. plantarum 200655 could be enhanced to obtain higher yields than that in MRS medium.
