Bioencapsulation of living yeast (Pichia pastoris) with silica after transformation with lysozyme gene

Bioencapsulation is an attractive way to immobilize biomolecules including cells, in silica or hybrid materials. Until now the sol-gel technology was preferentially utilized in bacteria or yeast cells immobilization. Biomimetic route to silica materials synthesis offers considerable advantages over conventional strategies. Recently, lysozyme has been used to induce the rapid synthesis of amorphous silica and it provides a convenient approach to synthesize silica under ambient temperature and pH. In this study, we showed that Pichia pastoris can be transformed with the gene encoding the losozyme. The heterologously produced lysozyme was enzymatically active, which was confirmed by measuring the bactericidal activity against Gram-positive bacteria and staining with Rhodamine 123 (formation of silica from silicic acid). Scanning electron microscopic analysis revealed that a viscous silica cover formed around the yeast in the presence of silicic acid. Furthermore, we demonstrated that the growth kinetics of P. pastoris was not affected after transformation when growing in the medium with silicic acid. In conclusion, yeast cells can be bioengineered to secrete lysozyme, which in turn conveniently mediate the encapsulation of yeast cells within silica. The facile method for yeast encapsulation may prove a novel way for cell immobilization through the combination of genetic approach and biomineralization.