Effect of pretreatment procedure on properties of Kombucha fermented bacterial cellulose membrane

Abstract

Abstract The article presents comparative analysis of bacterial cellulose membrane (BCM) structure and properties when pretreatment in water and in weak alkali solution (0.5%) is applied. BCM is obtained from Kombucha (identified as acetic acid bacteria Komagataeibacter xylinus and yeast Zygosaccharomyces bailli ) fermentation. Due to the presence of high amount of amorphous binding agents of growing medium the structure of the untreated BCM is bulky and crystallinity is low (29.10%). Experiments confirmed, that applying both pretreatment methods the medium can be washed out and neutralized cellulose material (pH ≈ 7) with higher crystallinity (47.00%) can be obtained after 8 h of low-polluting BCM washing. Washed samples showed higher thermal stability that can be assigned to the higher crystallinity and more pure cellulose form of BCM. FTIR analysis proved that the alkaline solution and water used in the BC washing has the influence on BCM structure changes: after pretreatment crystallinity peaks obtained more intensive, amorphous areas decreased and sugar was removed from the membrane. According to the higher thickness change after pretreatment, it was estimated that NaOH solutions penetration into the cellulose structure was higher than water, because in alkaline environment the substance sorts more water, therefore the properties of samples after both pretreatment procedures were very similar. By washing with no aggressive solutions bacterial cellulose membrane is prepared for further finishing treatment in order to obtain material for end use products.