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Aims: Obtain varieties of Gluconacetobacter hansenii from original strain ATCC 23729 with greater efficiency to produce bacterial cellulose (BC) membrane with better dry mass yield for application as support of sustained antimicrobials' drug release., Methods and Results: Application of different chemical and physical conditions (pH, temperature and UV light exposure) to obtain different G. hansenii varieties with high capacity to produce BC membranes. Characterization of the G. hansenii variants was performed by scanning electron microscopy (SEM) and optical microscopy of the colony-forming units. BC membrane produced was characterized by SEM, infrared spectroscopy and X-ray diffraction. The BC produced by variants isolated after incubation at 35°C showed elevated dry mass yield and high capacity of retention and sustained release of ceftriaxone antibiotic with the produced BC by original G. hansenii ATCC 23769 strain subjected to incubation at 28°C and with commercial BC., Conclusion: The application of different chemical and physical conditions constitutes an important method to obtain varieties of micro-organisms with dissimilar metabolism advantageous in relation to the original strain in the BC production., Significance and Impact of the Study: These results demonstrate the importance of in vivo studies for the application, in medicine, of BC membranes as support for antimicrobial-sustained release for the skin wound treatment., (© 2018 The Society for Applied Microbiology.)

Aims: The influence of bacterial species/strains in agitated culture was investigated on the morphology and structure characteristics of bacterial cellulose., Methods and Results: Komagataeibacter nataicola Y19 and Gluconacetobacter entanii ACCC10215 were inoculated in Hestrin-Schramm (HS) medium and subjected to agitated cultivation. Different kinds of BCs were obtained including flocky asterisk-like BC by G. entanii ACCC10215 and solid sphere-like BC by K. nataicola Y19. The SEM results showed that the asterisk-like BC had larger pores than the solid sphere-like BC. The FT-IR and X-ray diffraction results showed the asterisk-like BC had lower crystallinity (81·43%), higher cellulose Iα mass fraction (79·74%) and smaller crystallite size., Conclusions: The different species/strains can influence the morphology and structure characteristics of BC in agitated culture., Significance and Impact of the Study: We examined the influence of different species/strains on the morphology, macro- and microstructure of BCs produced in agitated culture for the first time, which suggest that different BCs with potential applications could be obtained by choosing different species or strains and fermentation method., (© 2014 The Society for Applied Microbiology.)

Production of 4-keto-D-arabonate (4KAB) was confirmed in a culture medium of Gluconacetobacter liquefaciens strains, newly isolated from water kefir in Argentina. The strains rapidly oxidized D-glucose, D-gluconate (GA), and 2-keto-D-gluconate (2KGA), and accumulated 2,5-diketo-D-gluconate (25DKA) exclusively before reaching the stationary phase. 25DKA was in turn converted to 4KAB, and 4KAB remained stable in the culture medium. The occurrence of 4KAB was assumed by Ameyama and Kondo about 50 years ago in their study on the carbohydrate metabolism of acetic acid bacteria (Bull. Agr. Chem. Soc. Jpn., 22, 271-272, 380-386 (1958)). This is the first report confirming microbial production of 4KAB.

Aim: The purpose of this work was to study the feasibility of producing economic flame retardant bacterial cellulose (BC) and evaluating its behaviour in paper production., Methods and Results: This type of BC was prepared by Gluconacetobacter subsp. xylinus and substituting the glucose in the cultivation medium by glucose phosphate as a carbon source; as well as using corn steep liquor as a nitrogen source. The investigated processing technique did not dispose any toxic chemicals that pollute the surroundings or cause unacceptable effluents, making the process environmentally safe. The fire retardant behaviour of the investigated BC has been studied by non-isothermal thermogravimetric analysis (TGA & DTGA). The activation energy of each degradation stage and the order of degradation were estimated using the Coats-Redfern equation and the least square method. Strength, optical properties, and thermogravimetric analysis of BC-phosphate added paper sheets were also tested., Conclusions: The study confirmed that the use of glucose phosphate along with glucose was significant in the high yield production of phosphate containing bacterial cellulose (PCBC1); more so than the use of glucose phosphate alone (PCBC2). Incorporating 5% of the PCBC with wood pulp during paper sheet formation was found to significantly improve kaolin retention, strength, and fire resistance properties as compared to paper sheets produced from incorporating bacterial cellulose (BC)., Significance and Impact of the Study: This modified BC is a valuable product for the preparation of specialized paper, in addition to its function as a fillers aid.

Aim: To examine the zinc (Zn) solubilization potential and nematicidal properties of Gluconacetobacter diazotrophicus., Methods and Results: Atomic Absorption Spectrophotometer, Differential Pulse Polarography and Gas Chromatography Coupled Mass Spectrometry were used to estimate the total Zn and Zn(2+) ions and identify the organic acids present in the culture supernatants. The effect of culture filtrate of Zn-amended G. diazotrophicus PAl5 on Meloidogyne incognita in tomato was examined under gnotobiotic conditions. Gluconacetobacter diazotrophicus PAl5 effectively solubilized the Zn compounds tested and 5-ketogluconic acid was identified as the major organic acid aiding the solubilization of zinc oxide. The presence of Zn compounds in the culture filtrates of G. diazotrophicus enhanced the mortality and reduced the root penetration of M. incognita under in vitro conditions., Conclusions: 5-ketogluconic acid produced by G. diazotrophicus mediated the solubilization process and the available Zn(2+) ions enhanced the nematicidal activity of G. diazotrophicus against M. incognita., Significance and Impact of the Study: Zn solubilization and enhanced nematicidal activity of Zn-amended G. diazotrophicus provides the possibility of exploiting it as a plant growth promoting bacteria.

Aim: The purpose of this study was to analyse the effects of different culture parameters on Gluconacetobacter hansenii (ATCC 10821) to determine which conditions provided optimum cellulose growth., Methods and Results: Five culture factors were investigated: carbon source, addition of ethanol, inoculation ratio, pH and temperature. jmp Software (SAS, Cary, NC, USA) was used to design this experiment using a fractional factorial design. After 22 days of static culture, the cellulose produced by the bacteria was harvested, purified and dried to compare the cellulose yields. The results were analysed by fitting the data to a first-order model with two-factor interactions., Conclusions: The study confirmed that carbon source, addition of ethanol, and temperature were significant factors in the production of cellulose of this G. hansenii strain. While pH alone does not significantly affect average cellulose production, cellulose yields are affected by pH interaction with the carbon source. Culturing the bacteria on glucose at pH 6.5 produces more cellulose than at pH 5.5, while using mannitol at pH 5.5 produces more cellulose than at pH 6.5. The bacteria produced the most cellulose when cultured on mannitol, at pH 5.5, without ethanol, at 20 degrees C. Inoculation ratio was not found to be a significant factor or involved in any significant two-factor interaction., Significance and Impact of the Study: These findings give insight into the conditions necessary to maximize cellulose production from this G. hansenii strain. In addition, this work demonstrates how the fractional factorial design can be used to test a large number of factors using an abbreviated set of experiments. Fitting a statistical model determined the significant factors as well as the significant two-factor interactions.

Nitrogen-fixing bacteria have been isolated from sugarcane in an endophytic and beneficial interaction that promotes plant growth. In this work, for the first time, the involvement of ethylene signalling in this interaction was investigated by molecular characterizing members of this pathway in sugarcane. The expression pattern of a putative ethylene receptor (SCER1) and two putative ERF transcription factors (SCERF1 and SCERF2) show exclusive modulation in plants inoculated with the diazotrophic endophytes. The gene expression profile of SCER1, SCERF1, and SCERF2 is differentially regulated in sugarcane genotypes that can establish efficient or inefficient associations with diazotrophic micro-organisms, exhibiting high or low biological nitrogen fixation (BNF) rates, respectively. In addition, SCER1, SCERF1, and SCERF2 expression is different in response to interactions with pathogenic and beneficial micro-organisms. Taken together, that data suggest that SCER1, SCERF1, and SCERF2 might participate in specific ethylene signalling cascade(s) that can identify a beneficial endophytic association, modulating sugarcane responses toward the diazotrophic endophytes.