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Enhanced production of bacterial cellulose by using a biofilm reactor and its material property analysis.

Cheng KC, Catchmark JM, Demirci A - J Biol Eng (2009)

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. kuc141@psu.edu

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

The TGA curves of BC samples produced on biofilm and suspended-cell reactor before (A) and after (B) removal of free water.
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Figure 6: The TGA curves of BC samples produced on biofilm and suspended-cell reactor before (A) and after (B) removal of free water.

Mentions: To determine water retention and information on thermal decomposition behavior of PCS-grown BC, thermogravimetric analysis (TGA) was performed on BC samples at the end of cultivation with and without PCS present. The TGA thermograms of BC samples are shown in Figure 6. PCS-grown BC exhibited around 95% water retention ability, which is lower than BC from the suspended-cell reactor (98%) (Figure 6A), but higher than a BC pellicle from static culture (73%) as reported earlier by Seifert et al. [32]. The results are probably due to incorporation of some water-insoluble particles of PCS, that alter the morphology of the BC structure (Figure 4C). For thermal decomposition behavior of BC samples, dried BC samples were used. Figure 6B showed two distinct steps for weight loss of BC samples, indicating the possibility of two types of decomposition. Yang and Chen [33] illustrated that the initial weight loss at lower temperature ranging from 200°C to 360°C is attributed to the removal of small molecular fragments such as hydroxyl and methylhydroxyl groups. The second weight loss ranging from 360°C to 600°C showed the degradation of polymeric chains and the six-member cyclic structure, pyran. Since the thermal degradation behavior is affected by some structure parameters such as molecular weight, crystallinity, and orientation [34], the more sharp decrease in weight of PCS-grown BC at both stages could be due to its higher crystallinity, degree of polymerization and compact interweaving structure. The maximum decomposition temperature (Tmax), known as a criterion of thermal decomposition position, was calculated from different TGA curves. Each peak on the Tmax pattern represents the steepest slope of weight loss (%/°C) for each step during decomposition. The PCS-grown BC displayed two peaks (Figure 7), one at 265°C and another at 445°C. In the cases of PCS-grown BC, the Tmax of first peak increased by about 30°C, which indicated PCS-grown BC possessed higher thermal stability and began to degrade at higher temperature.


Enhanced production of bacterial cellulose by using a biofilm reactor and its material property analysis.

Cheng KC, Catchmark JM, Demirci A - J Biol Eng (2009)

The TGA curves of BC samples produced on biofilm and suspended-cell reactor before (A) and after (B) removal of free water.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2724407&req=5

Figure 6: The TGA curves of BC samples produced on biofilm and suspended-cell reactor before (A) and after (B) removal of free water.
Mentions: To determine water retention and information on thermal decomposition behavior of PCS-grown BC, thermogravimetric analysis (TGA) was performed on BC samples at the end of cultivation with and without PCS present. The TGA thermograms of BC samples are shown in Figure 6. PCS-grown BC exhibited around 95% water retention ability, which is lower than BC from the suspended-cell reactor (98%) (Figure 6A), but higher than a BC pellicle from static culture (73%) as reported earlier by Seifert et al. [32]. The results are probably due to incorporation of some water-insoluble particles of PCS, that alter the morphology of the BC structure (Figure 4C). For thermal decomposition behavior of BC samples, dried BC samples were used. Figure 6B showed two distinct steps for weight loss of BC samples, indicating the possibility of two types of decomposition. Yang and Chen [33] illustrated that the initial weight loss at lower temperature ranging from 200°C to 360°C is attributed to the removal of small molecular fragments such as hydroxyl and methylhydroxyl groups. The second weight loss ranging from 360°C to 600°C showed the degradation of polymeric chains and the six-member cyclic structure, pyran. Since the thermal degradation behavior is affected by some structure parameters such as molecular weight, crystallinity, and orientation [34], the more sharp decrease in weight of PCS-grown BC at both stages could be due to its higher crystallinity, degree of polymerization and compact interweaving structure. The maximum decomposition temperature (Tmax), known as a criterion of thermal decomposition position, was calculated from different TGA curves. Each peak on the Tmax pattern represents the steepest slope of weight loss (%/°C) for each step during decomposition. The PCS-grown BC displayed two peaks (Figure 7), one at 265°C and another at 445°C. In the cases of PCS-grown BC, the Tmax of first peak increased by about 30°C, which indicated PCS-grown BC possessed higher thermal stability and began to degrade at higher temperature.

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. kuc141@psu.edu

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus