Improved viability of spray-dried Lactobacillus bulgaricus sp1.1 embedded in acidic-basic proteins treated with transglutaminase.

Spray drying is a fast and low-cost method of drying lactic acid bacteria, but it features a low survival rate. A pre-treatment was designed to increase the survival by embedding bacteria in basic or acidic proteins with the principle of opposite charges attraction. Transglutaminase (TGase)-induced cross-linking then tightened the cell-protein complexes. The results showed that mixing of basic proteins with acidic proteins and TGase treatment increased the survival rates of spray-dried Lactobacillus bulgaricus sp1.1. 84.78% of cells in the TGase-treated milk basic protein (MBP)-soy protein isolate (SPI) bacterial solution remained after drying. Positively charged MBP adhered to more bacteria (negative charge) and formed tight closed loop-shaped complexes with SPI (negative charge) by electrostatic attraction, and TGase enhanced this attraction by strengthening of the hydrogen, CO and CN bonds and exposing the inner α-helix. Imbedding bacteria in TGase-treated acidic-basic protein can increase efficiency of the current formulation.