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Transcriptional analysis of Amorphotheca resinae ZN1 on biological degradation of furfural and 5-hydroxymethylfurfural derived from lignocellulose pretreatment.

Wang X, Gao Q, Bao J - Biotechnol Biofuels (2015)

Bottom Line: During the detoxification process, A. resinae ZN1 firstly reduced furfural or HMF into furfuryl alcohol or HMF alcohol, and then oxidized into furoic acid or HMF acid through furan aldehyde as the intermediate at low concentration level.Two Zn-dependent alcohol dehydrogenase genes and five AKR/ARI genes were found to be responsible for the furfural and HMF conversion to their corresponding alcohols.The genes responsible for the furfural and HMF degradation to the corresponding alcohols and acids in A. resinae ZN1 were identified based on the analysis of the genome annotation, the gene transcription data and the inhibitor conversion results.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 China.

ABSTRACT

Background: Furfural and 5-hydroxymethylfurfural (HMF) are the two major inhibitor compounds generated from lignocellulose pretreatment, especially for dilute acid, steam explosion, neutral hot water pretreatment methods. The two inhibitors severely inhibit the cell growth and metabolism of fermenting strains in the consequent bioconversion step. The biodetoxification strain Amorphotheca resinae ZN1 has demonstrated its extraordinary capacity of fast and complete degradation of furfural and HMF into corresponding alcohol and acid forms. The elucidation of degradation metabolism of A. resinae ZN1 at molecular level will facilitate the detoxification of the pretreated lignocellulose biomass and provide the metabolic pathway information for more powerful biodetoxification strain development.

Results: Amorphotheca resinae ZN1 was able to use furfural or HMF as the sole carbon source for cell growth. During the detoxification process, A. resinae ZN1 firstly reduced furfural or HMF into furfuryl alcohol or HMF alcohol, and then oxidized into furoic acid or HMF acid through furan aldehyde as the intermediate at low concentration level. The cell mass measurement suggested that furfural was more toxic to A. resinae ZN1 than HMF. In order to identify the degradation mechanism of A. resinae ZN1, transcription levels of 137 putative genes involved in the degradation of furfural and HMF in A. resinae ZN1 were investigated using the real-time quantitative PCR (qRT-PCR) method under the stress of furfural and HMF, as well as the stress of their secondary metabolites, furfuryl alcohol and HMF alcohol. Two Zn-dependent alcohol dehydrogenase genes and five AKR/ARI genes were found to be responsible for the furfural and HMF conversion to their corresponding alcohols. For the conversion of the two furan alcohols to the corresponding acids, three propanol-preferring alcohol dehydrogenase genes, one NAD(P)(+)-depending aldehyde dehydrogenase gene, or two oxidase genes with free oxygen as the substrate were identified under aerobic condition.

Conclusions: The genes responsible for the furfural and HMF degradation to the corresponding alcohols and acids in A. resinae ZN1 were identified based on the analysis of the genome annotation, the gene transcription data and the inhibitor conversion results. These genetic resources provided the important information for understanding the mechanism of furfural and HMF degradation and modification of high tolerant strains used for biorefinery processing.

No MeSH data available.


Related in: MedlinePlus

Degradation of furfural (a) or HMF (b) with 5 g/L of glucose by A. resinae ZN1. Conditions: inoculum 10 % (v/v), 28 °C, natural pH in static state culture. Mean values are presented with error bars representing two standard deviations
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Fig3: Degradation of furfural (a) or HMF (b) with 5 g/L of glucose by A. resinae ZN1. Conditions: inoculum 10 % (v/v), 28 °C, natural pH in static state culture. Mean values are presented with error bars representing two standard deviations

Mentions: To accumulate enough cell mass of A. resinae ZN1 for qRT-PCR test, glucose was added as the carbon source together with furfural or HMF. Figure 3 shows that furfural and HMF were converted into furfuryl alcohol and HMF alcohol, respectively, but the glucose consumption and cell growth were very slow until furfural and HMF were decreased to a low level. The results indicate that the two furan aldehydes were prior to glucose as the substrates for A. resinae ZN1. Figure 3 also reveals the difference of furfural and HMF degradation in A. resinae ZN1 when glucose was added. For furfural, the presence of glucose did not affect the degradation rate of furfural to furfuryl alcohol, but the degradation of furfuryl alcohol to furoic acid was prolonged. The cell mass was increased to 2 g/L (Fig. 3a), approximately one order of magnitude greater than that without glucose addition (0.3 g/L). It was also observed that furoic acid concentration was very low although furfuryl alcohol was quickly decreased with glucose addition, indicating that furoic acid was metabolized quickly after its formation into the central carbon metabolism. For HMF, the presence of glucose surprisingly accelerated the conversion of HMF to HMF alcohol and the decrease of HMF approximately was equal to the increase of HMF alcohol (Fig. 3b). The conversion of HMF alcohol to HMF acid was accelerated only when glucose was almost degraded completely. The maximum cell mass with glucose existence was 1.2 g/L, almost threefolds greater than that without glucose addition.Fig. 3


Transcriptional analysis of Amorphotheca resinae ZN1 on biological degradation of furfural and 5-hydroxymethylfurfural derived from lignocellulose pretreatment.

Wang X, Gao Q, Bao J - Biotechnol Biofuels (2015)

Degradation of furfural (a) or HMF (b) with 5 g/L of glucose by A. resinae ZN1. Conditions: inoculum 10 % (v/v), 28 °C, natural pH in static state culture. Mean values are presented with error bars representing two standard deviations
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4559888&req=5

Fig3: Degradation of furfural (a) or HMF (b) with 5 g/L of glucose by A. resinae ZN1. Conditions: inoculum 10 % (v/v), 28 °C, natural pH in static state culture. Mean values are presented with error bars representing two standard deviations
Mentions: To accumulate enough cell mass of A. resinae ZN1 for qRT-PCR test, glucose was added as the carbon source together with furfural or HMF. Figure 3 shows that furfural and HMF were converted into furfuryl alcohol and HMF alcohol, respectively, but the glucose consumption and cell growth were very slow until furfural and HMF were decreased to a low level. The results indicate that the two furan aldehydes were prior to glucose as the substrates for A. resinae ZN1. Figure 3 also reveals the difference of furfural and HMF degradation in A. resinae ZN1 when glucose was added. For furfural, the presence of glucose did not affect the degradation rate of furfural to furfuryl alcohol, but the degradation of furfuryl alcohol to furoic acid was prolonged. The cell mass was increased to 2 g/L (Fig. 3a), approximately one order of magnitude greater than that without glucose addition (0.3 g/L). It was also observed that furoic acid concentration was very low although furfuryl alcohol was quickly decreased with glucose addition, indicating that furoic acid was metabolized quickly after its formation into the central carbon metabolism. For HMF, the presence of glucose surprisingly accelerated the conversion of HMF to HMF alcohol and the decrease of HMF approximately was equal to the increase of HMF alcohol (Fig. 3b). The conversion of HMF alcohol to HMF acid was accelerated only when glucose was almost degraded completely. The maximum cell mass with glucose existence was 1.2 g/L, almost threefolds greater than that without glucose addition.Fig. 3

Bottom Line: During the detoxification process, A. resinae ZN1 firstly reduced furfural or HMF into furfuryl alcohol or HMF alcohol, and then oxidized into furoic acid or HMF acid through furan aldehyde as the intermediate at low concentration level.Two Zn-dependent alcohol dehydrogenase genes and five AKR/ARI genes were found to be responsible for the furfural and HMF conversion to their corresponding alcohols.The genes responsible for the furfural and HMF degradation to the corresponding alcohols and acids in A. resinae ZN1 were identified based on the analysis of the genome annotation, the gene transcription data and the inhibitor conversion results.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 China.

ABSTRACT

Background: Furfural and 5-hydroxymethylfurfural (HMF) are the two major inhibitor compounds generated from lignocellulose pretreatment, especially for dilute acid, steam explosion, neutral hot water pretreatment methods. The two inhibitors severely inhibit the cell growth and metabolism of fermenting strains in the consequent bioconversion step. The biodetoxification strain Amorphotheca resinae ZN1 has demonstrated its extraordinary capacity of fast and complete degradation of furfural and HMF into corresponding alcohol and acid forms. The elucidation of degradation metabolism of A. resinae ZN1 at molecular level will facilitate the detoxification of the pretreated lignocellulose biomass and provide the metabolic pathway information for more powerful biodetoxification strain development.

Results: Amorphotheca resinae ZN1 was able to use furfural or HMF as the sole carbon source for cell growth. During the detoxification process, A. resinae ZN1 firstly reduced furfural or HMF into furfuryl alcohol or HMF alcohol, and then oxidized into furoic acid or HMF acid through furan aldehyde as the intermediate at low concentration level. The cell mass measurement suggested that furfural was more toxic to A. resinae ZN1 than HMF. In order to identify the degradation mechanism of A. resinae ZN1, transcription levels of 137 putative genes involved in the degradation of furfural and HMF in A. resinae ZN1 were investigated using the real-time quantitative PCR (qRT-PCR) method under the stress of furfural and HMF, as well as the stress of their secondary metabolites, furfuryl alcohol and HMF alcohol. Two Zn-dependent alcohol dehydrogenase genes and five AKR/ARI genes were found to be responsible for the furfural and HMF conversion to their corresponding alcohols. For the conversion of the two furan alcohols to the corresponding acids, three propanol-preferring alcohol dehydrogenase genes, one NAD(P)(+)-depending aldehyde dehydrogenase gene, or two oxidase genes with free oxygen as the substrate were identified under aerobic condition.

Conclusions: The genes responsible for the furfural and HMF degradation to the corresponding alcohols and acids in A. resinae ZN1 were identified based on the analysis of the genome annotation, the gene transcription data and the inhibitor conversion results. These genetic resources provided the important information for understanding the mechanism of furfural and HMF degradation and modification of high tolerant strains used for biorefinery processing.

No MeSH data available.


Related in: MedlinePlus