Produção e caracterização de celulose bacteriana em cultivo estático e agitado

Abstract

Bacterial cellulose (BC) is a biopolymer produced by fermentation by microorganisms. This material stands out for various applications because of its high crystallinity, high mechanical strength, biocompatibility, biodegradability, transparency and high chemical stability. When compared to cellulose of vegetable origin, CB is obtained with a high purity index by much simpler purification methods. The structural characteristics of BC are directly dependent on their synthesis conditions. In this work, three different strains were used in two culture forms (static and agitated) to produce BC by fermentation in Hestrin-Schramm (HS) synthetic medium. The strains used were Komagataeibacter (formerly Gluconacetobacter) xylinus ATCC 53582, Komagataeibacter hansenii ATCC 23769 and Komagataeibacter xylinus ATCC 700178. The produced CB was characterized by X-ray diffraction (DRX), Fourier Transform Infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry thermoporometry (TP-DSC). The highest production was achieved by K. xylinus ATCC 53582, with 1.4 g.L-1 for shake cultivation and 2.08 g.L-1 for static cultivation. The highest yields were also found for this strain, with 22% for static cultivation and 9% for agitated cultivation. The morphological difference between BCs produced in each culture form was evident. All moisture analysis results were greater than 99%, confirming the CB's high ability to retain water. In static culture, BC films were produced with the surface shape of the medium in which it was contained during the fermentation. In the agitated culture, fibrous pellets were formed. FTIR spectroscopy and TGA results found that the material produced is purified cellulose. The diffractograms show high crystallinity of the material. TGA results indicate a higher stability for CB obtained by agitated cultivation. TP-DSC results show pores with diameters mainly lower than 10 nm, but with polydispersed distribution.