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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

(A) Diagram of the PCS biofilm reactor, and (B) Cellulose grown on the PCS shaft after 120 hr cultivation.
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Figure 1: (A) Diagram of the PCS biofilm reactor, and (B) Cellulose grown on the PCS shaft after 120 hr cultivation.

Mentions: BC fermentations were conducted in a 1.25-L Bioflo 3000 fermentor (New Brunswick Scientific, Edison, NJ) at 30°C with a working volume of 1 L and the agitation rate of 100 rpm. For the biofilm reactor, 12 PCS tubes were bound to the agitator shaft in a gridlike fashion, with 6 rows of two parallel tubes (Figure 1). The reactor vessel with PCS was autoclaved with water at 121°C for 45 min. Fructose and nitrogenous components with mineral salts were autoclaved separately and added to the reactor aseptically after draining the water from the reactor as recommended by Ho et al. [24]. After inoculation with a 24-h culture of A. xylinum (10% v/v), 120-h batch fermentation was carried out. The initial pH was set at 5.0, but pH was not controlled during fermentation. After each run, the biomass on the PCS, BC production, and residual fructose were evaluated. Suspended-cell fermentation as control (i.e. without PCS) was conducted using the same protocol except that the reactor containing medium without PCS was autoclaved and inoculated with 24-h culture of A. xylinum (10% v/v) at the beginning of each batch. Each treatment was duplicated.


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)

(A) Diagram of the PCS biofilm reactor, and (B) Cellulose grown on the PCS shaft after 120 hr cultivation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: (A) Diagram of the PCS biofilm reactor, and (B) Cellulose grown on the PCS shaft after 120 hr cultivation.
Mentions: BC fermentations were conducted in a 1.25-L Bioflo 3000 fermentor (New Brunswick Scientific, Edison, NJ) at 30°C with a working volume of 1 L and the agitation rate of 100 rpm. For the biofilm reactor, 12 PCS tubes were bound to the agitator shaft in a gridlike fashion, with 6 rows of two parallel tubes (Figure 1). The reactor vessel with PCS was autoclaved with water at 121°C for 45 min. Fructose and nitrogenous components with mineral salts were autoclaved separately and added to the reactor aseptically after draining the water from the reactor as recommended by Ho et al. [24]. After inoculation with a 24-h culture of A. xylinum (10% v/v), 120-h batch fermentation was carried out. The initial pH was set at 5.0, but pH was not controlled during fermentation. After each run, the biomass on the PCS, BC production, and residual fructose were evaluated. Suspended-cell fermentation as control (i.e. without PCS) was conducted using the same protocol except that the reactor containing medium without PCS was autoclaved and inoculated with 24-h culture of A. xylinum (10% v/v) at the beginning of each batch. Each treatment was duplicated.

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