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Effects of aromatic compounds on the production of bacterial nanocellulose by Gluconacetobacter xylinus.

Zhang S, Winestrand S, Guo X, Chen L, Hong F, Jönsson LJ - Microb. Cell Fact. (2014)

Bottom Line: However, very little is known about the effect on G. xylinus of specific lignocellulose-derived inhibitors.Vanillin was reduced to vanillyl alcohol with a yield of up to 80%.This is the first investigation of the effect of specific phenolics on the production of BC by G. xylinus, and is also the first demonstration of the ability of G. xylinus to convert phenolic compounds.

View Article: PubMed Central - HTML - PubMed

Affiliation: China-Sweden Associated Research Laboratory in Industrial Biotechnology, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China. fhong@dhu.edu.cn.

ABSTRACT

Background: Bacterial cellulose (BC) is a polymeric nanostructured fibrillar network produced by certain microorganisms, principally Gluconacetobacter xylinus. BC has a great potential of application in many fields. Lignocellulosic biomass has been investigated as a cost-effective feedstock for BC production through pretreatment and hydrolysis. It is well known that detoxification of lignocellulosic hydrolysates may be required to achieve efficient production of BC. Recent results suggest that phenolic compounds contribute to the inhibition of G. xylinus. However, very little is known about the effect on G. xylinus of specific lignocellulose-derived inhibitors. In this study, the inhibitory effects of four phenolic model compounds (coniferyl aldehyde, ferulic acid, vanillin and 4-hydroxybenzoic acid) on the growth of G. xylinus, the pH of the culture medium, and the production of BC were investigated in detail. The stability of the phenolics in the bacterial cultures was investigated and the main bioconversion products were identified and quantified.

Results: Coniferyl aldehyde was the most potent inhibitor, followed by vanillin, ferulic acid, and 4-hydroxybenzoic acid. There was no BC produced even with coniferyl aldehyde concentrations as low as 2 mM. Vanillin displayed a negative effect on the bacteria and when the vanillin concentration was raised to 2.5 mM the volumetric yield of BC decreased to ~40% of that obtained in control medium without inhibitors. The phenolic acids, ferulic acid and 4-hydroxybenzoic acid, showed almost no toxic effects when less than 2.5 mM. The bacterial cultures oxidized coniferyl aldehyde to ferulic acid with a yield of up to 81%. Vanillin was reduced to vanillyl alcohol with a yield of up to 80%.

Conclusions: This is the first investigation of the effect of specific phenolics on the production of BC by G. xylinus, and is also the first demonstration of the ability of G. xylinus to convert phenolic compounds. This study gives a better understanding of how phenolic compounds and G. xylinus cultures are affected by each other. Investigations in this area are useful for elucidating the mechanism behind inhibition of G. xylinus in lignocellulosic hydrolysates and for understanding how production of BC using lignocellulosic feedstocks can be performed in an efficient way.

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Cultivation of G. xylinus in medium containing coniferylaldehyde. The figure shows changes in (A) the glucose concentrationin the culture medium, (B) the pH value of the culture medium, (C)the concentration of living cells, and (D) the concentration of coniferylaldehyde. Coniferyl aldehyde was added on day one. Error bars show standard errorsof means of three replicates.
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Figure 2: Cultivation of G. xylinus in medium containing coniferylaldehyde. The figure shows changes in (A) the glucose concentrationin the culture medium, (B) the pH value of the culture medium, (C)the concentration of living cells, and (D) the concentration of coniferylaldehyde. Coniferyl aldehyde was added on day one. Error bars show standard errorsof means of three replicates.

Mentions: Results from cultivations of G. xylinus in the presence of coniferyl aldehydeare shown in Figure 2 and Table 1.The glucose consumption rates in cultures with initial concentrations of coniferylaldehyde of 0.5 mM, 1.0 mM and 1.5 mM were3.5 g/[L · d], 3.4 g/[L · d] and2.8 g/[L · d], respectively. This was relatively close to theglucose consumption rate of the culture with reference medium, which was3.5 g/[L · d] (Table 1A), although aslight inhibition was observed at concentrations of 1.0 and 1.5 mM coniferylaldehyde. At 2.0 mM coniferyl aldehyde, the glucose consumption rate droppeddrastically to 0.45 g/[L · d]. The concentration of live bacteriadecreased as the concentration of coniferyl aldehyde increased (Figure 2C). At the end of the cultivation, the pH decreased to 2.8, whichwas the same as for the reference medium, except for cultures with 2.0 mM coniferylaldehyde for which there was not much change in pH (Figure 2B). For cultures with 0.5-1.5 mM coniferyl aldehyde, the volumetric yieldof BC was in the range 3.4-6.4 g/L, which was lower than that of the culture withreference medium (6.7 g/L) (Table 1B). No BC productionwas detected in cultures with 2.0 mM coniferyl aldehyde. The yield of BC onconsumed glucose showed the same trend. Increasing coniferyl aldehyde concentrationsfrom 0.5 to 1.5 mM resulted in a decrease of the yield of BC from 0.26 to0.17 g/g, while the reference medium gave a BC yield of 0.28 g/g(Table 1C). At the end of the cultivation, all coniferylaldehyde was converted except for cultures with an initial concentration of coniferylaldehyde of 2 mM where most of it remained (Figure 2D).


Effects of aromatic compounds on the production of bacterial nanocellulose by Gluconacetobacter xylinus.

Zhang S, Winestrand S, Guo X, Chen L, Hong F, Jönsson LJ - Microb. Cell Fact. (2014)

Cultivation of G. xylinus in medium containing coniferylaldehyde. The figure shows changes in (A) the glucose concentrationin the culture medium, (B) the pH value of the culture medium, (C)the concentration of living cells, and (D) the concentration of coniferylaldehyde. Coniferyl aldehyde was added on day one. Error bars show standard errorsof means of three replicates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4126184&req=5

Figure 2: Cultivation of G. xylinus in medium containing coniferylaldehyde. The figure shows changes in (A) the glucose concentrationin the culture medium, (B) the pH value of the culture medium, (C)the concentration of living cells, and (D) the concentration of coniferylaldehyde. Coniferyl aldehyde was added on day one. Error bars show standard errorsof means of three replicates.
Mentions: Results from cultivations of G. xylinus in the presence of coniferyl aldehydeare shown in Figure 2 and Table 1.The glucose consumption rates in cultures with initial concentrations of coniferylaldehyde of 0.5 mM, 1.0 mM and 1.5 mM were3.5 g/[L · d], 3.4 g/[L · d] and2.8 g/[L · d], respectively. This was relatively close to theglucose consumption rate of the culture with reference medium, which was3.5 g/[L · d] (Table 1A), although aslight inhibition was observed at concentrations of 1.0 and 1.5 mM coniferylaldehyde. At 2.0 mM coniferyl aldehyde, the glucose consumption rate droppeddrastically to 0.45 g/[L · d]. The concentration of live bacteriadecreased as the concentration of coniferyl aldehyde increased (Figure 2C). At the end of the cultivation, the pH decreased to 2.8, whichwas the same as for the reference medium, except for cultures with 2.0 mM coniferylaldehyde for which there was not much change in pH (Figure 2B). For cultures with 0.5-1.5 mM coniferyl aldehyde, the volumetric yieldof BC was in the range 3.4-6.4 g/L, which was lower than that of the culture withreference medium (6.7 g/L) (Table 1B). No BC productionwas detected in cultures with 2.0 mM coniferyl aldehyde. The yield of BC onconsumed glucose showed the same trend. Increasing coniferyl aldehyde concentrationsfrom 0.5 to 1.5 mM resulted in a decrease of the yield of BC from 0.26 to0.17 g/g, while the reference medium gave a BC yield of 0.28 g/g(Table 1C). At the end of the cultivation, all coniferylaldehyde was converted except for cultures with an initial concentration of coniferylaldehyde of 2 mM where most of it remained (Figure 2D).

Bottom Line: However, very little is known about the effect on G. xylinus of specific lignocellulose-derived inhibitors.Vanillin was reduced to vanillyl alcohol with a yield of up to 80%.This is the first investigation of the effect of specific phenolics on the production of BC by G. xylinus, and is also the first demonstration of the ability of G. xylinus to convert phenolic compounds.

View Article: PubMed Central - HTML - PubMed

Affiliation: China-Sweden Associated Research Laboratory in Industrial Biotechnology, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620, China. fhong@dhu.edu.cn.

ABSTRACT

Background: Bacterial cellulose (BC) is a polymeric nanostructured fibrillar network produced by certain microorganisms, principally Gluconacetobacter xylinus. BC has a great potential of application in many fields. Lignocellulosic biomass has been investigated as a cost-effective feedstock for BC production through pretreatment and hydrolysis. It is well known that detoxification of lignocellulosic hydrolysates may be required to achieve efficient production of BC. Recent results suggest that phenolic compounds contribute to the inhibition of G. xylinus. However, very little is known about the effect on G. xylinus of specific lignocellulose-derived inhibitors. In this study, the inhibitory effects of four phenolic model compounds (coniferyl aldehyde, ferulic acid, vanillin and 4-hydroxybenzoic acid) on the growth of G. xylinus, the pH of the culture medium, and the production of BC were investigated in detail. The stability of the phenolics in the bacterial cultures was investigated and the main bioconversion products were identified and quantified.

Results: Coniferyl aldehyde was the most potent inhibitor, followed by vanillin, ferulic acid, and 4-hydroxybenzoic acid. There was no BC produced even with coniferyl aldehyde concentrations as low as 2 mM. Vanillin displayed a negative effect on the bacteria and when the vanillin concentration was raised to 2.5 mM the volumetric yield of BC decreased to ~40% of that obtained in control medium without inhibitors. The phenolic acids, ferulic acid and 4-hydroxybenzoic acid, showed almost no toxic effects when less than 2.5 mM. The bacterial cultures oxidized coniferyl aldehyde to ferulic acid with a yield of up to 81%. Vanillin was reduced to vanillyl alcohol with a yield of up to 80%.

Conclusions: This is the first investigation of the effect of specific phenolics on the production of BC by G. xylinus, and is also the first demonstration of the ability of G. xylinus to convert phenolic compounds. This study gives a better understanding of how phenolic compounds and G. xylinus cultures are affected by each other. Investigations in this area are useful for elucidating the mechanism behind inhibition of G. xylinus in lignocellulosic hydrolysates and for understanding how production of BC using lignocellulosic feedstocks can be performed in an efficient way.

Show MeSH
Related in: MedlinePlus