Strains

Agricultural residues are constantly increasing with increased farming processes, and improper disposal is detrimental to the environment. Majority of these waste residues are rich in lignocellulose, which makes them suitable substrate for bacterial fermentation in the production of value-added products. In this study, bacterial cellulose (BC), a purer and better form of cellulose, was produced by two Komagataeibacter sp. isolated from rotten banana and kombucha drink using corncob (CC) and sugarcane bagasse (SCB) enzymatic hydrolyzate, under different fermentation conditions, that is, static, continuous, and intermittent agitation. The physicochemical and mechanical properties of the BC films were then investigated by Fourier Transformed Infrared Spectroscopy (FTIR), Thermogravimetry analysis, Field Emission Scanning Electron Microscopy (FE-SEM), and Dynamic mechanical analysis. Agitation gave a higher BC yield, with Komagataeibacter sp. CCUG73629 producing BC from CC with a dry weight of 1.6 g/L and 1.4 g/L under continuous and intermittent agitation, respectively, compared with that of 0.9 g/L in HS medium. While BC yield of dry weight up to 1.2 g/L was obtained from SCB by Komagataeibacter sp. CCUG73630 under continuous agitation compared to that of 0.3 g/L in HS medium. FTIR analysis showed BC bands associated with cellulose I, with high thermal stability. The FE-SEM analysis showed that BC fibers were highly ordered and densely packed. Although the BC produced by both strains showed similar physicochemical and morphological properties, the BC produced by the Komagataeibacter sp. CCUG73630 in CC under intermittent agitation had the best modulus of elasticity, 10.8 GPa and tensile strength, 70.9 MPa.

Genetic modification for enhancing bacterial cellulose production and its applications

Bacterial cellulose (BC) is higher in demand due to its excellent properties which is attributed to its purity and nano size. Komagataeibacter xylinum is a model organism where BC production has been studied in detail because of its higher cellulose production capacity. BC production mechanism shows involvement of a series of sequential reactions with enzymes for biosynthesis of cellulose. It is necessary to know the mechanism to understand the involvement of regulatory proteins which could be the probable targets for genetic modification to enhance or regulate yield of BC and to alter BC properties as well. For the industrial production of BC, controlled synthesis is desired so as to save energy, hence genetic manipulation opens up avenues for upregulating or controlling the cellulose synthesis in the bacterium by targeting genes involved in cellulose biosynthesis. In this review article genetic modification has been presented as a tool to introduce desired changes at genetic level resulting in improved yield or properties. There has been a lack of studies on genetic modification for BC production due to limited availability of information on whole genome and genetic toolkits; however, in last few years, the number of studies has been increased on this aspect as whole genome sequencing of several Komagataeibacter strains are being done. In this review article, we have presented the mechanisms and the targets for genetic modifications in order to achieve desired changes in the BC production titer as well as its characteristics.