3.1. Lactic Acid Production from the Repeated-Batch and SSF of SCW
The profiles of lactic acid and starch concentrations of the repeated-batch and SSF of SCW by L.
plantarum MSUL 702 are shown in Fig. 1.
The highest lactic acid concentration at 28.71 g/L was produced in the 48 h of the first batch fermentation while the starch was mostly consumed.
The concentration of lactic acid produced was higher than those obtained by [9] which carried out SSF of raw starch by Streptococcus bovis 148.
It was also higher than the study of [10] and [11] which conducted SSF of cassava starch by L.
amylovorus ATCC 33620 and L. rhamnosus, respectively.
However, in the subsequent batches, a reduction of lactic acid production and a longer starch consumption time were observed.
The highest lactic acid concentrations in batch 2-5 ranged from 28.39 g/L to 20.29 g/L.
These results could be due to the lower cell concentrations in the SCW (Fig. 2).
The effects of product inhibition could be another caused of the reduction of lactic acid production [12].
In the fifth batch, lactic acid production was markedly reduced.
Thus, the next batch was ceased.
As shown in Fig. 2, the viable LAB and biomass concentration were in concordant to the results of lactic acid production.
The highest viable LAB and biomass concentration at 9.26 log CFU/mL and 3,183.33 mg/L,
respectively, were obtained in 48 h of the first batch fermentation.
A high viable LAB (higher than 8.0 log CFU/mL) was attained until batch 3.
After that, the cells were decreased dramatically which might be due to the adverse effects of product inhibition and the contamination since the experiments were conducted under a nonsterile
condition.
In the 72 h of the fifth batch fermentation, a residual starch in the SCW was presence and the