Characterization and optimization of bacterial cellulose produced by Acetobacter spp.

im: The study aimed to search for a potential bacterial strain capable of producing maximal bacterial cellulose under optimized conditions for future scale up.Methodology: Eight cellulose producing bacterial strains were isolated from sugarcane juice using Hestrin and Schramm (HS) medium. These isolates were identified through 16S rDNA based on molecular phylogenetic approach and the cellulose mat was analyzed for their physico-chemical properties. Morphological, chemical and physical properties of cellulose mat was studied by Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy spectrum, High Performance Liquid Chromotograpy and Differential Scanning Calorimetry. Optimal nutrient composition for maximum cellulose production by the isolate was carried out by response surface methodology.Results: 16S rDNA sequence analysis revealed that the isolates belonged to Acetobacter senegalensis, Acetobacter thailandicus, Acetobacter lambici, Acetobacter lovaniensis and Acinetobacter baumannii. Among them, A. senegalensis MA1 produced the maximum cellulose mat of dry weight 3.6 g per 500 ml of HS medium after 2 weeks of incubation. The morphology of bacterial cellulose produced by A. senegalensis MA1 had a pellicle shaped distinguished network structure and the rod shaped bacterium was attached to the bottom of cellulose mat. HPLC analysis revealed that the peaks obtained from bacterial cellulose were almost similar to carboxymethyl cellulose (CMC) peak. In cellulose mat, the weight of carbon, oxygen were 60.13 and 25.12, respectively. Analysis of differential scanning calorimetry showed endothermal peak at 139.8°C., indicating the melting point of bacterial cellulose mat. Through response surface methodology analysis, 5 g of glycerol and 1.2 g of yeast extract per 100 ml medium was optimized to get maximum cellulose production (2.04 g) from A. senegalensis MA1. Interpretation: Optimized condition for maximum bacterial cellulose production may be applied at industrial scale for commercial utilization

Dynamic changes of total acid and bacterial communities during the traditional fermentation of Hong Qu glutinous rice wine

Background: Hong Qu glutinous rice wine (HQGRW) is brewed under non-aseptic fermentation conditions, so it usually has a relatively high total acid content. The aim of this study was to investigate the dynamics of the bacterial communities and total acid during the fermentation of HQGRW and elucidate the correlation between total acid and bacterial communities. Results: The results showed that the period of rapid acid increase during fermentation occurred at the early stage of fermentation. There was a negative response between total acid increase and the rate of increase in alcohol during the early fermentation stage. Bacterial community analysis using high-throughput sequencing technology was found that the dominant bacterial communities changed during the traditional fermentation of HQGRW. Both principal component analysis (PCA) and hierarchical clustering analysis revealed that there was a great difference between the bacterial communities of Hong Qu starter and those identified during the fermentation process. Furthermore, the key bacteria likely to be associated with total acid were identified by Spearman's correlation analysis. Lactobacillus, unclassified Lactobacillaceae, and Pediococcus were found, which can make significant contributions to the total acid development (| r| N 0.6 with FDR adjusted P b 0.05), establishing that these bacteria can associate closely with the total acid of rice wine. Conclusions: This was the first study to investigate the correlation between bacterial communities and total acid during the fermentation of HQGRW. These findings may be helpful in the development of a set of fermentation techniques for controlling total acid.

Surface Film Formation in Static-Fermented Rice Vinegar: A Case Study

In the present study, we aimed to determine the cause of surface film formation in three rice vinegars fermented using the traditional static fermentation method. The pH and total acidity of vinegar were 3.0–3.3 and 3.0–8.7%, respectively, and acetic acid was the predominant organic acid present. Colonies showing a clear halo on GYC medium were isolated from the surface film of all vinegars. Via 16S rDNA sequencing, all of the isolates were identified as Acetobacter pasteurianus. Furthermore, field-emission scanning electron microscopy analysis showed that the bacterial cells had a rough surface, were rod-shaped, and were ∼1 × 2 µm in size. Interestingly, cells of the isolate from one of the vinegars were surrounded with an extremely fine threadlike structure. Thus, our results suggest that formation of the surface film in rice vinegar was attributable not to external contamination, to the production of bacterial cellulose by A. pasteurianus to withstand the high concentrations of acetic acid generated during fermentation. However, because of the formation of a surface film in vinegar is undesirable from an industrial perspective, further studies should focus on devising a modified fermentation process to prevent surface film formation and consequent quality degradation.

Modeling the kinetics of pyrite ash biodesulfurization by Saccharomyces cerevisiae and Acetobacter aceti in liquid state bioreactors

Background: Modeling the kinetics of the biodesulphurization bioprocess for the refining of pyrite ash by Saccharomyces cerevisiae and Acetobacter aceti have been studied in batch-type liquid- state bioreactors. Results: The biodesulphurization experiments were performed at varying temperatures of 25ºC, 30ºC and 35ºC for eight weeks. Glucose, acetic acid and ethyl alcohol were used in the incubation media as substrates and acid sources. pH and oxidation reduction potential (ORP) observations have been determined weekly and the dissolved sulphur was measured at the end of the eight weeks trials. An equation calculating pH was derived from the iron oxidation reaction containing the ferric to ferrous iron [Fe+3/Fe+2] ratio as a variable. The Michaelis-Menten predictive specific growth rates (qFe+2), which were estimated from pH and ORP observations, were compared by plotting [qFe+²]pH vs. [qFe+2]mV. The highest ratio of dissolved sulphur over total sulphur (Sd/St) was found to be 0.5 in the biodesulphurization processes. Conclusions: The model provides predictions of ferric to ferrous iron rates and specific growth rates [qFe+²]pH vs. [qFe+2]mV and can be used for the determination of oxidized and reduced ions. The ratios of dissolved sulphur to total sulphur (Sd/St) have shown some promising results for S. cerevisiae to be used as a biodesulphurization and refining microorganism for pyrite ash and the other sulphide minerals.

Minerals consumption by Acetobacter xylinum on cultivation medium on coconut water

The objective of this work is to verifying the consume of the minerals K, Na, Fe, Mg, P, S-SO4-2,B,N Total Kjedahl (NTK), NO3--N, and NH4+-N in the production of bacterial cellulose by Acetobacter xylinum, according to the medium and the manner of cultivation. The fermentative process was in ripe and green coconut water. K and Na were determined by flame emission photometry, Mg and Fe by atomic absorption spectrophotometry, P by molecular absorption spectrophotometry, S-SO4-2 by barium sulphate turbidimetry, B by Azomethin-H method, NTK by Kjeldahl method, N-NO3-and N-NH4+ by vapor distillation with magnesium oxide and Devarda's alloy, respectively. In Fermentation of ripe coconut water there were higher consumption of K (69%), Fe (84,3%), P (97,4%), S-SO2-2 (64,9%), B (56,1%), N-NO3 (94,7%) and N-NH4+ (95,2%), whereas coconut water of green fruit the most consumed ions were Na (94,5%), Mg (67,7%) and NTK (56,6%). The cultivation under agitation showed higher mineral consumption. The higher bacterial cellulose production, 6 g.L-1, was verified in the coconut water fermentative in ripe fruit, added KH2PO4, FeSO4 and NaH2PO4 kept under agitation.

Optimum Culture Conditions for Bacterial Cellulose Produced by Acetobacter xylinum NUST4 / 微生物学通报

The optimum culture conditions for Acetobacter xylinum NUST4 which produces bacterial cellulose(BC) were obtained by uniform design method.BC production was dependent on MgSO_(4)?7H_(2)O,FeSO_(4)?7H_(2)O and cosubstrates such as p-aminobenzoic acid,nicotinamide,d-Biotin and ethanol.The optimal medium contained glucose 24g,sucrose 22g,peptone 16g,HAc 2.4mL,Na_(2)HPO_(4)?12H_(2)O 3.5 g,KH_(2)PO_(4)?H_(2)O 1 g,MgSO_(4)?7H_(2)O 6 g,FeSO_(4)?7H_(2)O 0.015g,nicotinamide 0.003 g,d-Biotin 0.02g and ethanol 20mL in 1L culture medium.BC yield reached 9.87g(the dried weight) in stationary culture for 7 days,which was 12-fold higher than that in the S-H medium.