Characterization of cellulose production by a Gluconacetobacter xylinus strain from Kombucha

The aims of this work were to characterize and improve cellulose production by a Gluconoacetobacter xylinus strain isolated from Kombucha and determine the purity and some structural features of the cellulose from this strain. Cellulose yield in tea medium with both black tea and green tea and in Hestrin and Schramm (HS) medium under both static and agitated cultures was compared. In the tea medium, the highest cellulose yield was obtained with green tea (approximately 0.20 g/L) rather than black tea (approximately 0.14 g/L). Yield in HS was higher (approximately 0.28 g/L) but did not differ between static and agitated incubation. (1)H-NMR and (13)C-NMR spectroscopy indicated that the cellulose is pure (free of acetan) and has high crystallinity, respectively. Cellulose yield was improved by changing the type and level of carbon and nitrogen source in the HS medium. A high yield of approximately 2.64 g/L was obtained with mannitol at 20 g/L and corn steep liquor at 40 g/L in combination. In the tea medium, tea at a level of 3 g/L gave the highest cellulose yield and the addition of 3 g/L of tea to the HS medium increased cellulose yield to 3.34 g/L. In conclusion, the G. xylinus strain from Kombucha had different cellulose-producing characteristics than previous strains isolated from fruit. Cellulose was produced in a pure form and showed high potential applicability. Our studies extensively characterized cellulose production from a G. xylinus strain from Kombucha for the first time, indicating both similarities and differences to strains from different sources

Enhanced Production of Antimicrobial Compounds by Three Salt-Tolerant Actinobacterial Strains Isolated from the Sundarbans in a Niche-Mimic Bioreactor

A novel reactor system, the rotating disk bioreactor (RDBR), was used to mimic the niche environmental conditions of three salt-tolerant estuarine actinobacteria isolated from the Sundarbans region off the Bay of Bengal, designated MS310 (99% similar in its 16S rRNA gene sequence to Streptomyces parvallus), MS3/20 and MS1/7. The RDBR, operated at a rotational speed of one revolution per day, 50% submergence of discs, aeration rate of 1.0 vvm, and with a sucrose-containing medium, faithfully mimicked the intertidal estuarine habitat of these marine isolates, and supported biofilm formation and production of antimicrobial metabolites—in particular, actinomycin D by MS310. Onset of antibiotic production by MS310 occurs at 20 h in the RDBR compared to 55 h in a conventional stirred-tank bioreactor (STBR). Furthermore, peak antimicrobial activity is attained much earlier in the RDBR with MS310 (at 45 h) than that reported with a terrestrial strain of S. parvallus grown in a STBR (at 144 h). Peak antimicrobial activity of metabolites produced by MS1/7 and MS3/20 were also attained earlier in the RDBR (at 25 and 12 h, respectively) than in a STBR (at 80 and 28 h, respectively). Antibiotic synthesis in the three isolates, in general, appears to be associated with their growth. Overall, the RDBR may be considered the preferred alternative to the STBR for production of antimicrobials by biofilm-forming estuarine bacteria for its much higher surface/volume ratio, lower costs, and easy operability