No abstract

Complex nutrients e.g. carbon, nitrogen, peptides, vitamin and salts significantly play important roles in lactic acid production efficiency depending on types of microorganism and sources of raw material. In this study oil palm trunk juice and Lactobacillus rhamnosus TISTR 108 (ATTC 10863) were utilized for lactic acid production. Additional nutrients including peptone, yeast extract and mixed salts were tested. Response surface methodology involving Box Behkhen Design (BBD) was applied to examine the optimal condition. Prediction of optimization was performed using full quadratic regression equation. The predicted maximum lactic acid concentration was obtained at 64.05 g•l −1 within a period of 48 h under an optimal condition of 10 g•l −1 peptone with mixed salts containing 0.4 g•l −1 MgSO 4 •7H 2 O, 0.1 g•l −1 MnSO 4 •4H 2 O, 3 g•l −1 K 2 HPO 4 , 3 g•l −1 KH 2 PO 4 and 3 g•l −1 CH 3 COONa•3H 2 O in 250 ml shake flask using CaCO 3 as a titrant. Verification of optimization condition was performed in 2 l fermenter using Ca(OH) 2 as neutralizing agent. Increase in lactic acid fermentation was achieved at 92.81 g•l −1 at 48 h cultivation. The lactic acid yield and volumetric productivity were 0.94 g•g −1 and 1.91 g l −1 •h −1 , respectively. This suggests that OPT juice is potentially used as carbon and nutrient sources for lactic acid production.

The cost of fermentable sugars added as a substrate is one major problem for economic lactic acid (LA) production. Old oil palm trunks (OPT) squeezed sap, the agricultural wastes on replanting and pruning of oil palm (Elaeis guineensis), contained mainly glucose and fructose as a potential feedstock to use as a vast carbon source for LA production. To improve the LA yield and productivity, various fermentation modes were performed by Lactobacillus rhamnosus ATCC 10863 using OPT sap as a basal medium. A modified constant feed mode of fed-batch and repeated fed-batch fermentation using undiluted OPT sap feed medium can achieve a high average LA concentration of 95.94 g/L, yield of 1.04 g/g, and productivity of 6.40 g/L/h) at 11 h cultivation time. It can also provide open and open repeated batch fermentation with an average LA concentration of 91.30 g/L, yield of 0.87 g/g, and productivity of 3.88 g/L/h at 21 h fermentation time.

Salted eggs are normally produced by treating fresh duck eggs with a high salt concentration in order to acquire distinctive features and excellent preservation capabilities as a result of a series of physicochemical changes. This method, however, induces a high salt content in the product. The goal of this research was to create a new way of producing mildly salted duck eggs using ozonized brine salting. The brine was made by dissolving NaCl (26% w/v) in water or ozonized water at a concentration of 50 ng ozone/mL (ozonized brine). Compared to brine, ozonized brine resulted in salted eggs with reduced ultimate salt levels in both albumen and yolk (p < 0.05). The Haugh unit of the salted eggs generated by ozonized brine was similar to that of the brine-made salted egg group (p > 0.05), but the salted egg produced by ozonized brine matured and solidified faster because the yolk index (0.62) was higher than that of the brine (0.55) (p < 0.05). The final pH of salted eggs generated with brine and ozonized brine was not different (p > 0.05). Regardless of the salting method, both salted eggs contained low TVB-N content (<10 mg/100 g). Ozonized brine increased the protein carbonyl content in salted albumen, which may be related to albumen protein aggregation and served as a salt diffusion barrier. However, after boiling the salted egg, the protein carbonyl level was comparable to that of fresh albumen. The TBARS levels of boiled salted albumen prepared with brine and ozonized brine were comparable (p > 0.05), and the value was extremely low (~0.1 mg MDA equivalent/kg). The TBARS value of the salted yolk prepared with brine was higher than that of the salted yolk prepared with ozonized brine (p < 0.05), and both salted yolks showed increased TBARS values after cooking (p < 0.05). The albumen and yolk components appeared to be altered similarly by both brine and ozonized brine, according to the FTIR spectra. Furthermore, the appearance and color of the yolk and albumen in salted eggs prepared with brine and ozonized brine were comparable. Boiled salted albumen produced with ozonized brine had a denser structure with fewer voids. This could be attributed to the final salted egg’s lower salt content and lower salt diffusion rate, which were likely caused by protein oxidation and, as a result, aggregation when ozonized brine was used.