Yanji Wang

Effects of temperature and trehalose on foam separation of nisin from the culture broth produced by Lactococcus lactis subspecies lactis W28

Nisin is an antimicrobial peptide, an important biopreservative, and it is produced by certain strains of Lactococcus lactis ssp. lactis. In this paper, a foam separation technique was used for the separation of nisin from its culture broth, and the effects of temperature and trehalose on the performance of foam separation of nisin were studied to increase the enrichment ratio and recovery percentage of nisin and decrease the inactivity percentage of nisin. The results showed that temperature and trehalose significantly affected the performance of foam separation of nisin. Under the optimum conditions of 50°C temperature, 150-mL/min air flow rate, 400-mL initial loading liquid volume, and 1-g/L trehalose concentration, the maximum enrichment ratio, recovery percentage, and the minimum inactivity percentage of nisin reached 23.7, 84.1%, and 5.9%, respectively, which were, respectively, 5.04, 0.93, and 1.03 times more than those under the conditions of 20°C temperature, 150-mL/min air flow rate, 400-mL initial loading liquid volume, and no trehalose addition. These results indicated that the change of temperature and the addition of trehalose could improve the performance of foam separation of nisin.

Role of foam drainage in producing protein aggregates in foam fractionation

It is essential to obtain a clear understanding of the foam-induced protein aggregation to reduce the loss of protein functionality in foam fractionation. The major effort of this work is to explore the roles of foam drainage in protein aggregation in the entire process of foam fractionation with bovine serum albumin (BSA) as a model protein. The results show that enhancing foam drainage increased the desorption of BSA molecules from the gas-liquid interface and the local concentration of desorbed molecules in foam. Therefore, it intensified the aggregation of BSA in foam fractionation. Simultaneously, it also accelerated the flow of BSA aggregates from rising foam into the residual solution along with the drained liquid. Because enhancing foam drainage increased the relative content of BSA molecules adsorbed at the gas-liquid interface, it also intensified the aggregation of BSA during both the defoaming process and the storage of the foamate. Furthermore, enhancing foam drainage more readily resulted in the formation of insoluble BSA aggregates. The results are highly important for a better understanding of foam-induced protein aggregation in foam fractionation.

β-Cyclodextrin preventing protein aggregation in foam fractionation of bovine serum albumin

In this work, β-cyclodextrin was developed to prevent protein aggregation in foam fractionation using bovine serum albumin (BSA) as a model protein. The role of β-cyclodextrin in preventing the aggregation of BSA induced by the gas-liquid interface was studied at the molecular level. The results indicate that by holding the exposed phenylalanine residues in its hydrophobic cavity, β-cyclodextrin effectively prevented the aggregation of BSA induced by the gas-liquid interface in foam fractionation. Furthermore, β-cyclodextrin could be effectively separated from BSA in the foamate due to their weak association.

A novel technology coupling extraction and foam fractionation for separating the total saponins from Achyranthes bidentata

ABSTRACT A novel technology coupling extraction and foam fractionation was developed for separating the total saponins from Achyranthes bidentata. In the developed technology, the powder of A. bidentata was loaded in a nylon filter cloth pocket with bore diameter of 180 µm. The pocket was fixed in the bulk liquid phase for continuously releasing saponins. Under the optimal conditions, the concentration and the extraction rate of the total saponins in the foamate by the developed technology were 73.5% and 416.2% higher than those by the traditional technology, respectively. The foamates obtained by the traditional technology and the developed technology were analyzed by ultraperformance liquid chromatography–mass spectrometry to determine their ingredients, and the results appeared that the developed technology exhibited a better performance for separating saponins than the traditional technology. The study is expected to develop a novel technology for cost effectively separating plant-derived materials with surface activity.