Abstract
The use of bacterial cellulose (BC) in food systems is still limited due to production costs. Nine clones belonging to Komagataeibacter hansenii, Komagataeibacter nataicola, Komagataeibacter rhaeticus, Komagataeibacter swingsii, and Komagataeibacter xylinus species were screened for cellulose productivity in growth tests with five different carbon sources and three nitrogen sources. The water-holding and rehydration capacities of the purified cellulose were determined. The structure of the polymer was investigated through nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy and X-ray diffraction (XRD) analysis, and observed by scanning electron microscope (SEM). Natural mutants of K. rhaeticus LMG 22126T and K. swingsii LMG 22125T showed different productivity. The factors “bacterial isolate” and “nitrogen source” significantly affected the production of cellulose (p < 0.01) rather than the factor “carbon source” (p = 0.15). However, on average, the best conditions for increasing yield were found in medium containing glucose and peptone. Water-holding capacity (WHC) values ranged from 10.7 to 42.3 (gwater/gcellulose) with significant differences among strains (p < 0.01), while the rehydration capacity varied from 4.2 to 9.3 (gwater/gcellulose). A high crystallinity (64–80%) was detected in all samples with Iα fractions corresponding to 67–93%. The ATR-FT-IR spectra and the XRD patterns confirmed the expected structure. BC made by GVP isolate of K. rhaeticus LMG 22126T, which was the strain with the highest yield, was added to a gluten-free bread formulation. Results obtained from measurements of technological parameters in dough leavening and baking trials were promising for implementation in potential novel foods.
Highlights
In food technology, cellulose and its derivatives obtained after partial etherification with different groups, are approved additives coded from E460 to E469 (Commission Regulation, 2012), used for their thickening, anti-caking, gelling, and stabilizing properties
The type strains of five Komagataeibacter species, which are considered the highest producers of cellulose, and other isolates were selected
The isolate GVP of K. rhaeticus LMG 22126T was the highest producer of bacterial cellulose (BC), while K. hansenii LMG 1527T gave rise to a type of polymer with a promising rehydration capacity, potentially useful for food applications
Summary
Cellulose and its derivatives obtained after partial etherification with different groups, are approved additives coded from E460 to E469 (Commission Regulation, 2012), used for their thickening, anti-caking, gelling, and stabilizing properties. Acetic acid bacteria that synthesize it belong to the risk group 1 according to the German TRBA classification (Federal Institute for Occupational Safety and Health, 2010). These microorganisms and their extracellular products are naturally present in various traditional foods with a long history of safety for human consumption, like kombucha (Gomes et al, 2018; Villarreal-Soto et al, 2018), nata (Dourado et al, 2017; Zhang et al, 2017), water kefir (Gulitz et al, 2011), lambic beer (De Roos and De Vuyst, 2018), and numerous kinds of vinegars and liquors (Gullo and Giudici, 2008; Štornik et al, 2016). Since BC productivity is generally low for making it an economically acceptable process for industrial implementation, selection for better performing strains and assessment of the most efficient conditions for cellulose synthesis are still under study (Campano et al, 2016; Chen et al, 2018)
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