Production of bacterial cellulose by Gluconacetobacter hansenii CGMCC 3917 using only waste beer yeast as nutrient source

In order to improve the use of waste beer yeast (WBY) for bacterial cellulose production by Gluconacetobacter hansenii CGMCC 3917, a two-step pre-treatment was designed. First WBY was treated by 4 methods: 0.1 M NaOH treatment, high speed homogenizer, ultrasonication and microwave treatment followed by hydrolysis (121 °C, 20 min) under mild acid condition (pH 2). The optimal pre-treatment conditions were evaluated by the reducing sugar yield after hydrolysis. 15% WBY treated by ultrasonication for 40 min had the highest reducing sugar yield (29.19%), followed by NaOH treatment (28.98%), high speed homogenizer (13.33%) and microwaves (13.01%). Treated WBY hydrolysates were directly supplied as only nutrient source for BC production. A sugar concentration of 3% WBY hydrolysates treated by ultrasonication gave the highest BC yield (7.02 g/L), almost 6 times as that from untreated WBY (1.21 g/L). Furthermore, the properties of the BC were as good as those obtained from the conventional chemical media.