No abstract

The ability of rice protein supplemented with various prebiotics to protect probiotic Lactobacillus plantarum TISTR 2075 upon freeze-drying and subsequent storage was determined. A combination of rice proteinfructooligosaccharide (RF) provided the best storage stability with the lowest specific rate of cell death (k) of 1.20 9 10-2 and 5.79 9 10-2 1/day during subsequent storage at 4°C for 180 days and 30°C for 90 days, respectively. Glass transition temperatures (T g) of freezedried probiotic in various protectants were 14.2-25.4 and 42.9-50.1°C after storage at 4 and 30°C, respectively. The functional properties of freeze-dried probiotic with protectants remained stable. The presence of RF could effectively protect and enhance the probiotic functionality during exposure to gastrointestinal tract conditions. The pathogenic inhibition of freeze-dried probiotic against foodborne pathogens was not different from the active cells. Protective agents were able to maintain high degrees of cell surface hydrophobicity.

It is generally known that both chemical substances and many kinds of microorganism can be used to produce surfactants or surface-active compounds. Surfactants derived from microorganisms are called biosurfactants, or bio-surface active compounds. Recently, biosurfactants have become more interesting because of their advantages, such as less toxicity and more degradability, which cannot be found in traditional surfactants. Biosurfactant production faces some problems, such as a high cost of production. In the medical field, biosurfactants are attractive, because the products from biosurfactants can be used effectively in small amounts. This can compensate for the high cost of production. In addition, there have been many great discoveries of biosurfactants in the medical field.

Palm pressed fiber (PPF) is a clean and renewable lignocellulosic material. The PPF and delignified PPF (DPPF) were used as a carrier for immobilization of Candida shehatae TISTR5843 in bioethanol production. PPF was pre-treated by milling to obtain small particles, whereas DPPF was the delignification of PPF using NaClO2. C. shehatae TISTR5843 was grown in modified yeast extractmalt (YM) medium at 30 ± 2ºC on an orbital shaker at 150 rpm for batch and repeated batch fermentation. In the batch system, immobilized cells on a small size, less than 0.5 mm, of DPPF (sDPPF) gave the maximum ethanol production of 11.5 g L -1 at 24 hrs cultivation period. The ethanol concentration and ethanol yield of sDPPF were 6.2% and 6.8% higher (ethanol production 11.5 g L -1 , ethanol yield 0.47 g g -1 ) than those of free cells (ethanol production 10.8 g L -1 , ethanol yield 0.44 g g -1 ) after 36 hrs of cultivation. In contrast, the small size of PPF (sPPF) was selected as a carrier in repeated batch fermentation for cost effectiveness. The ethanol productivity of immobilized yeast cells in repeated batch fermentations was 45.2-51.6% greater than that obtained from batch fermentations. The immobilized cells on sPPF improved the ethanol production and could be reused 4 times with retaining the activity of 93%. In conclusion, PPF is a potential carrier in the immobilization system. The pre-treatment of PPF increases the surface area that enhances cell adsorption and ethanol production by C. shehatae TISTR5843.