Abstract: For improved protective effect of sodium alginate (SA) beads on lactic acid bacteria (LAB) exposed to simulated gastrointestinal fluid (SGF), soybean cellulose nanocrystals (SCNC) or cellulose nanofibrils (SCNF), both of which were prepared from soybean okara, in combination with SA was used to encapsulate LAB with calcium ions as a cross-linker. The microstructure of SA-nanocellulose beads was observed, Fourier transform infrared spectroscopy and low frequency nuclear magnetic resonance were analyzed. The effect of SA-nanocellulose beads on the viability of LAB in SGF was investigated by determining the number of viable bacteria before and after gastrointestinal digestion. Nanocellulose could increase the encapsulation efficiency of SA beads and decrease the surface pores. In addition, SCNF was better than SCNC in improving the hydrogen bonding capacity of SA, promoting the formation of a salt bridge between the SA chain and Ca2+, strengthening the structure of the gel network, and ultimately enhancing the mechanical strength of SA beads. Furthermore, SA-SCNF beads provided better protection of LAB after exposure to SGF with a reduction in viable cell count of 1.51 (lg(CFU/g)), significantly lower than that observed for SA beads (2.99 (lg(CFU/g))) and SA-SCNC beads (2.16 (lg(CFU/g))) (P < 0.05). These results indicated that SCNF can be applied as a nano-carrier for the encapsulation of LAB to keep it stable in the gastrointestinal tract.

Key words: sodium alginate; cellulose; nanofibrils; nanocrystals; probioticd; simulated gastrointestinal fluid