CHEMICAL CHARACTERIZATION OF BACTERIAL CELLULOSE PRODUCED BY Komagataeibacter sp. V-05 FROM SOYBEAN MOLASSES

Bacterial cellulose (BC) is a polysaccharide of repeating units of β-D-glucose that exhibits higher physico-chemical and mechanical properties than the cellulose obtained from vegetable sources. CB exhibits higher purity and crystallinity index, higher degree of polymerization, better water absorption and retention, higher tensile strength, higher elasticity and biocompatibility. This work aimed to characterize BC membranes produced by an acetic acid bacteria previously isolated from a vinegar industry and identified as Komagataeibacter sp. V-05, using a soybean industry co-product, named soybean molasses, and the standard Hestrin-Schramm (HS), as substrate. For this, 10% of the inoculum was transferred to Erlenmeyers either containing 90 mL of soybean molasses diluted at 20º Brix added of 2% ethanol to improve the productivity or containing 90 mL of HS broth. The flasks were incubated at 30 ºC for 14 days under static conditions. After this, the membranes produced in the surface of the media were heated to 80 °C / 30 min. with alkaline solution (1M NaOH) and then, rinsed to neutral pH with distillated water. The dried membranes at 60 °C were chemically characterized by X-ray diffraction (Panalytical X'Pert PRO MPD), thermogravimetric analysis (TGA) (Shimadzu TGA 50) and infrared spectroscopy (FT-IR Bommen MB-100). The TGA curves of the membranes presented three distinct stages of mass loss that are characteristic of CB. The membranes produced from HS medium had the highest temperature required to the initial thermal degradation (307 ºC), which may be correlated with the higher uniplanarity and the higher crystallinity index of these samples (71.6%), requiring higher energy for its degradation. On the other hand, the membranes produced in soybean molasses had slightly lower values for initial thermal degradation and crystallinity index, 299.3 ºC and 69%, respectively. Both samples presented infrared bands that are characteristics of CB, such as stretching vibrations at 3500 cm-1, 2900 cm-1, 2700 cm-1, 1600 cm-1, 1400 cm-1, 1370 cm-1, 1340 cm-1 and at 1320-1030 cm-1. The X-ray diffraction data demonstrated that the culture medium did not influence the crystal organization of the membranes. Both samples had two main peaks at 15º and 22.5º which demonstrate that the samples possess typical crystalline forms of cellulose I. Based on this, it was possible to conclude that the soybean molasses can be an interesting and economic alternative for CB production, since it was maintained the structural characteristics similar to those obtained from HS medium.