A study on the influence of surface area-to-volume (S/V) ratio on production of bacterial cellulose in a static-batch fermenter

Effect of co-culture of Komagataeibacter nataicola and selected Lactobacillus fermentum on the production and characterization of bacterial cellulose

To reduce the cost of bacterial cellulose (BC) production, the possibility of using acetone-butanol-ethanol (ABE) fermentation wastewater with high COD value (18050mgl(-1) ) for BC production by Gluconacetobacter xylinus was evaluated. After 7days of fermentation, the highest BC yield (1·34gl(-1) ) was obtained. The carbon sources including sugars (glucose and xylose), organic acids (acetic acid and butyric acid) and alcohol compounds (ethanol and butanol) were utilized by G.xylinus simultaneously during fermentation. Although the COD decrease ratio (about 14·7%) was low, the highest BC yield on COD consumption (56·2%, gg(-1) ) was relatively high and the remaining wastewater could be used for further BC fermentation. Besides, the environment of ABE fermentation wastewater showed small influence on the BC structure by comparison with the BC products obtained in traditional HS medium using field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Overall, ABE fermentation wastewater is one promising substrate for BC production. The possibility of using acetone-butanol-ethanol (ABE) fermentation wastewater for bacterial cellulose (BC) production by Gluconacetobacter xylinus was evaluated in this study. This is the first time that ABE fermentation wastewater was used as substrate for BC fermentation. The results provide detail information of metabolism of G.xylinus in ABE fermentation wastewater and the influence of wastewater environment on the structure of BC samples. Overall, this bioconversion could reduce the cost of BC production greatly.

In this study, loquat extract was selected as a promising substrate for bacterial cellulose (BC) production. A new BC-producing bacterial strain was isolated from residual loquat and identified as Komagataeibacter rhaeticus. BC production with different carbon sources and with loquat extract was investigated. Among all tested carbon sources, glucose was demonstrated to be the best substrate for BC production by K. rhaeticus, with up to 7.89g/L dry BC obtained under the optimal initial pH (5.5) and temperature (28°C) with 10days of fermentation. The total sugar and individual sugars were investigated in different loquat extracts, in which fructose, glucose, and sucrose were the three main sugars. When loquat extract was prepared with a solid‒liquid (S-L) ratio of 2:1, the concentrations of glucose, fructose, and sucrose were 7.91g/L, 9.31g/L, and 2.84g/L, respectively. The BC production obtained from loquat extract was higher than that of other carbon sources except glucose, and 6.69g/L dry BC was obtained from loquat extract with an S-L ratio of 2:1. After BC production, all sugars substantially decreased, with the utilization of glucose, fructose, and sucrose reaching 93.9%, 87.9%, and 100%, respectively. These results suggested that the different sugars in loquat extract were all carbon sources participating in BC production by K. rhaeticus. Structural and physicochemical properties were investigated by SEM, TGA, XRD, and FT-IR spectroscopy. The results showed that the structural, chemical group, and water holding capacity of BC obtained from loquat extract were similar to those of BC obtained from glucose, but the crystallinity and thermal stability of BC were higher than those of BC from mannose and lactose but lower than those of BC from glucose and fructose. KEY POINTS: • A new BC-producing strain was isolated and identified as Komagataeibacter rhaeticus. • Loquat extract is an alternative substrate for BC production. • The BC obtained from loquat extract owns advanced physicochemical properties.

Culture conditions in a jar fermentor for bacterial cellulose (BC) production from A. xylinum BPR2001 were optimized by statistical analysis using Box-Behnken design. Response surface methodology was used to predict the levels of the factors, fructose (X1), corn steep liquor (CSL) (X2), dissolved oxygen (DO) (X3), and agar concentration (X4). Total 27 experimental runs by combination of each factor were carried out in a 10-L jar fermentor, and a three-dimensional response surface was generated to determine the effect of the factors and to find out the optimum concentration of each factor for maximum BC production and BC yield. The fructose and agar concentration highly influenced the BC production and BC yield. However, the optimum conditions according to changes in CSL and DO concentrations were predicted at almost central values of tested ranges. The predicted results showed that BC production was 14.3 g/L under the condition of 4.99% fructose, 2.85% CSL, 28.33% DO, and 0.38% agar concentration. On the other hand, BC yield was predicted in 0.34 g/g under the condition of 3.63% fructose, 2.90% CSL, 31.14% DO, and 0.42% agar concentration. Under optimized culture conditions, improvement of BC production and BC yield were experimentally confirmed, which increased 76% and 57%, respectively, compared to BC production and BC yield before optimizing the culture conditions.

Search for efficient low-cost substrate/additives are gaining significant impetus in bacterial cellulose (BC) production. Makgeolli sludge (a traditional Korean wine distillery waste) is enriched with organic acid, alcohol, and sugar. Using makgeolli sludge filtrate (MSF) and Hestrin-Schramm (HS) medium (g/l of distilled water: glucose, 10.0; peptone, 5.0; yeast extract, 5.0; disodium phosphate, 2.7; citric acid, 1.15; pH 5.0), two different media-namely the modified HS media (ingredients of HS media except glucose dissolved in MSF) and mixed modified HS media (equal volume mixture of original and modified HS media)-were formulated. BC production with Gluconacetobacter xylinus was studied using the two above referred medium. Keeping HS medium as reference, effect of initial pH, glucose, ethanol, and organic acid concentration on BC production was also studied. It suggests that increasing initial glucose (up to 25 g/l) though improves BC production but results in poor BC yield above 15 g/l of glucose. However, addition of alcohol (up to 1%v/v) or citric acid (up to 20 mM) escalate productivity up to four and two times, respectively. In both modified HS media and mixed modified HS medium, BC production was four to five times higher than that of original HS medium. Even MSF alone surpassed HS medium in BC production. Scanning electron microscopy showed that BC microfibrils from MSF based media were several micrometers long and about 25-60 nm widths. X-ray diffraction patterns suggested the produced BC were of cellulose I polymorph.

Bacterial cellulose has been used in the food industry for applications such as low-calorie desserts, salads, and fabricated foods. It has also been used in the paper manufacturing industry to enhance paper strength, the electronics industry in acoustic diaphragms for audio speakers, the pharmaceutical industry as filtration membranes, and in the medical field as wound dressing and artificial skin material. In this study, different types of plastic composite support (PCS) were implemented separately within a fermentation medium in order to enhance bacterial cellulose (BC) production by Acetobacter xylinum. The optimal composition of nutritious compounds in PCS was chosen based on the amount of BC produced. The selected PCS was implemented within a bioreactor to examine the effects on BC production in a batch fermentation. The produced BC was analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Among thirteen types of PCS, the type SFYR+ was selected as solid support for BC production by A. xylinum in a batch biofilm reactor due to its high nitrogen content, moderate nitrogen leaching rate, and sufficient biomass attached on PCS. The PCS biofilm reactor yielded BC production (7.05 g/L) that was 2.5-fold greater than the control (2.82 g/L). The XRD results indicated that the PCS-grown BC exhibited higher crystallinity (93%) and similar crystal size (5.2 nm) to the control. FESEM results showed the attachment of A. xylinum on PCS, producing an interweaving BC product. TGA results demonstrated that PCS-grown BC had about 95% water retention ability, which was lower than BC produced within suspended-cell reactor. PCS-grown BC also exhibited higher Tmax compared to the control. Finally, DMA results showed that BC from the PCS biofilm reactor increased its mechanical property values, i.e., stress at break and Young's modulus when compared to the control BC. The results clearly demonstrated that implementation of PCS within agitated fermentation enhanced BC production and improved its mechanical properties and thermal stability.

Bacterial cellulose (BC) is a biopolymer with a wide range of potential applications starting from the food industry and biomedicine to electronics and cosmetics. Despite that, BC industrial production to date still is associated with certain difficulties. One of them is the high cost of growth media, which can reach up to 30% of production costs. To decrease production costs, use of industrial and agricultural by-products, including whey, as alternative growth media has been reported. Whey, as the main high-volume by-product of dairy industry, which is known for its low valorisation opportunities and negative environmental impact, can nevertheless be considered as an alternative growth medium for BC production. To date, several studies aimed at evaluating BC production on whey and lactose substrates have been reported, but they are still insufficient. Reviews of them showed that, in general, BC production on untreated whey- and lactose-containing media was lower than that on the standard medium. However, some wild and recombinant strains have been reported to produce BC on whey as good as the standard medium. Enzymatic and acidic pre-treatment of whey significantly enhanced BC yield. Changes in the microstructure of BC obtained from whey were also recognised, which should be considered regarding the impact on physical properties of the desired BC product. This mini-review indicates that currently whey can be recognised as quite a problematic alternative growth substrate for industrial BC production; however, further extensive studies may improve the prospects in both the search for a cheap alternative growth substrate for industrial BC production and valorisation of whey. KEY POINTS: • Whey is a by-product in which valorisation is still challenging. • Whey can be used for bacterial cellulose (BC) production. • BC yield and properties vary upon cultivation conditions and producer strains.

Effect of media components on cell growth and bacterial cellulose production from Acetobacter aceti MTCC 2623

This study aimed to use waste figs as an alternative substrate for bacterial cellulose (BC) production by Komagataeibacter xylinus and optimize the identified process parameters to maximize the concentration of BC. Among the nutrients screened by Plackett–Burman (PB) design, yeast extract was found to be significant in BC production. Response surface methodology was used to investigate the effect of fermentation parameters on BC production. A maximum BC concentration of (8.45 g/L), which is among the highest BC concentrations reported so far, was achieved at the optimum levels of fermentation variables (initial pH 6.05, initial sugar concentration 62.75 g/L, temperature 30 °C). The utilization of response surface methodology (RSM) proved valuable in both optimizing and finding the interactions between process variables during BC production. Scanning electron microscope (SEM) analysis showed a dense structure of BC, characterized by ribbon-like nanofibrils with diameters ranging from 23 to 90 nm while the attenuated total reflection–Fourier transform infrared (ATR-FTIR) spectrum of BC confirmed that the material obtained was cellulose. The X-ray diffraction (XRD) analysis showed that the crystallinity of the BC samples was 70% for BC produced on waste fig medium and 61% for BC produced on Hestrin–Schramm (HS) medium. This is the first detailed study on the production of BC from waste figs, and the findings of this study demonstrated that waste figs can be used as an effective substrate for the production of BC.

In order to improve bacterial cellulose (BC) production yield by increasing the cell density, a new fermentation system using a spin filter was developed and its performance characteristics were tested. Fermentations were carried out in a fermenter equipped with a 6 flat-blade turbine impeller and a spin filter consisting of a cylinder surrounded by stainless steel mesh and whose stainless steel bottom was attached to the agitator shaft. This new fermentation assembly was tested under different experimental conditions for BC production by Gluconacetobacter hansenii PJK. In periodical perfusion culture without pH control, the BC production and the total cell mass increased with the culture time to 3.07 and 5.65 g/L, respectively, at 140 h of cultivation. The BC production was also tested at adjusted pH and pH 5 was found optimum for maximum BC production. At pH 5, in periodical perfusion culture, the BC production and the total cell mass reached to 4.57 and 11.52 g/L, respectively, after 140 h of cultivation. This amount of BC production was 2.9 times higher than that obtained in a conventional jar fermenter. The productivity improved and was 0.044 g/L·h at 68 h of cultivation.

Effects of glucuronic acid oligomers on the production, structure and properties of bacterial cellulose

To offset the negative effects of aeration on bacterial cellulose (BC) production by acetic acid bacteria using enmeshed cellulose microfibrils (CM) on luffa sponge matrices (LSM). The CM were enmeshed on LSM (LSM-CM). The optimal amount of LSM-CM was determined for BC production under aerated conditions. Without LSM-CM, no BC was produced in seven out of nine production cycles at the highest aeration rate (9lmin-1 ). However, with 0·5% LSM-CM and an aeration rate of 3lmin-1 , a satisfactory oxygen transfer coefficient was achieved, and also a good yield of BC (5·24gl-1 ). Moreover, the LSM-CM was able to be recycled through nine consecutive BC production cycles. The highest BC yields (from 5·8±0·4 to 6·6±0·4gl-1 ) were associated with high bacterial biomass and this was confirmed by scanning electron microscopy. We confirm that LSM-CM works well as a starter. Microenvironments low in dissolved oxygen within the matrices of LSM-CM are important for BC production under aeration conditions. The LSM-CM provides a microenvironment which offsets the negative effects of aeration on BC production. A sustainable, economic process for mass BC production is described using recycled LSM-CM with aeration.

Many studies have been concerned with nanocellulose's potential to produce environmentally friendly nanomaterial fibers. Bacterial cellulose has shown superiority over plant cellulose, leading to increased research focus on bacterial cellulose production. Among bacterial species, Acetobacter, particularly Komagataeibacter (formerly Gluconacetobacter), has captured interest due to its enhanced bacterial cellulose (BC) production and strain stability. Optimizing production processes becomes imperative with the growing demand for BC in various industries. This study explores the optimization of physical conditions for BC production using Komagataeibacter sucrofermentans. Five parameters—pH, temperature, aeration rate, shaking rate, and surface area, were examined using the One-factor-at-a-time (OFAT) method. This method was selected as it is useful in early-stage optimization to understand the effect of individual factors on BC production. The extracted BC was purified with 4.0 M NaOH solution at 80°C, and wet and dry weights were measured. Analysis via ANOVA determined the significance of each parameter in enhancing BC yield. Optimized conditions from this experiment —pH 5, temperature 20°C, 60% aeration rate, slow agitation (50 rpm), and large surface area fermentation (63.62 cm2) shown to give better BC production. These findings have substantial implications for enhancing BC production efficiency on an industrial scale.

Evaluation of detoxified sugarcane bagasse hydrolysate by atmospheric cold plasma for bacterial cellulose production

A single sugar α-linked glucuronic acid based oligosaccharide (SSGO) is water soluble oligosaccharides (WSOS) obtained by Gluconacetobacter hansenii PJK (KCTC 10505BP) as a byproduct during bacterial cellulose (BC) production. In this study, SSGO was used for the improvement of BC production by the vinegar bacterium, Acetobacter xylinum, which produces heteropolysaccharides as a byproduct. The addition of 1.0% SSGO to the chemically defined medium (CDM) resulted in an 89.3% increase in BC production by A. xylinum after 15 days of cultivation under static condition, and a 52.3% increase in BC production by G. hansenii. Both the dry cell weight and live cell density of A. xylinum increased 50% with the addition of 1.0% SSGO. SSGO successfully improved BC production by A. xylinum.