Abstract: In order to utilize rice milk effectively and reduce its discharge amount, the differences in the physicochemical indexes between rice milk and naturally fermented coconut water were compared, and the correlation analysis within physicochemical indexes and bacterial cellulose (BC) yield was conducted. The BC production based on rice milk medium was optimized, and some physical properties and chemical composition of the produced BC were investigated. The results showed that the contents of fructose, glucose, sucrose, acetic acid and protein in rice milk were significantly (P<0.05) lower than those in the naturally fermented coconut water, and these substances affected BC yield significantly (P<0.05). The optimal fermentation condition for rice milk was as follows: 35.0 g·L^-1 glucose as carbon source, and mixture of 3.0 g·L^-1 yeast extract and 3.0 g·L^-1 tryptone as nitrogen source. After optimization, the BC yield could reach 9.3 g·L^-1 (dry weight). BCs produced from either rice milk or the naturally fermented coconut water had nano-porous microstructure, and there was no significant difference in the water content, water holding capacity and hardness between them. Infrared spectroscopy and X-ray diffraction analysis showed that BCs produced from either rice milk or the naturally fermented coconut water were composed of β-glucan and type Ⅰ_α cellulose, and the crystallinity was 82.7% and 84.6%, respectively, indicating that BCs produced from rice milk and the naturally fermented coconut water were almost the same. Therefore, rice milk would be a promising material to produce BC.

Key words: rice milk, Gluconacetobacter xylinus, bacterial cellulose, microstructure, chemical composition