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Production of cellobionate from cellulose using an engineered Neurospora crassa strain with laccase and redox mediator addition.

Hildebrand A, Kasuga T, Fan Z - PLoS ONE (2015)

Bottom Line: By adding low concentrations of laccase and a redox mediator to the fermentation, CDH can be efficiently oxidized by the redox mediator, with in-situ re-oxidation of the redox mediator by laccase.The conversion of cellulose to cellobionate was optimized by evaluating pH, buffer, and laccase and redox mediator addition time on the yield of cellobionate.This paper describes a working concept of cellobionate production from cellulose using the CDH-ATBS-laccase system in a fermentation system.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Agricultural Engineering, University of California, Davis, One Shields Avenue, Davis, CA, 95616, United States of America.

ABSTRACT
We report a novel production process for cellobionic acid from cellulose using an engineered fungal strain with the exogenous addition of laccase and a redox mediator. A previously engineered strain of Neurospora crassa (F5∆ace-1∆cre-1∆ndvB) was shown to produce cellobionate directly from cellulose without the addition of exogenous cellulases. Specifically, N. crassa produces cellulases, which hydrolyze cellulose to cellobiose, and cellobiose dehydrogenase (CDH), which oxidizes cellobiose to cellobionate. However, the conversion of cellobiose to cellobionate is limited by the slow re-oxidation of CDH by molecular oxygen. By adding low concentrations of laccase and a redox mediator to the fermentation, CDH can be efficiently oxidized by the redox mediator, with in-situ re-oxidation of the redox mediator by laccase. The conversion of cellulose to cellobionate was optimized by evaluating pH, buffer, and laccase and redox mediator addition time on the yield of cellobionate. Mass and material balances were performed, and the use of the native N. crassa laccase in such a conversion system was evaluated against the exogenous Pleurotus ostreatus laccase. This paper describes a working concept of cellobionate production from cellulose using the CDH-ATBS-laccase system in a fermentation system.

No MeSH data available.


Related in: MedlinePlus

Enzymatic oxidation of substrate (cellobiose/lactose) by CDH.The reduced CDH is oxidized by a redox mediator (ABTS), which is in turn oxidized by laccase. The reduced laccase is oxidized by oxygen, with water as the only byproduct.
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pone.0123006.g001: Enzymatic oxidation of substrate (cellobiose/lactose) by CDH.The reduced CDH is oxidized by a redox mediator (ABTS), which is in turn oxidized by laccase. The reduced laccase is oxidized by oxygen, with water as the only byproduct.

Mentions: Baminger et al. reported a novel CDH-ABTS-laccase bi-enzyme system for fast oxidation of lactose to LBA [12]. Laccases are important multicopper oxidases which are also widely distributed in wood degrading fungi [13]. They are especially prevalent in white rot and brown rot fungi, with speculative involvement in lignin degradation [14]. In contrast to CDH, laccases oxidize a large number of reduced substances and use oxygen as the final electron acceptor very efficiently. One strategy to increase the rate of lactose oxidation by CDH with oxygen as the final electron acceptor is to employ catalytic amounts of DCPIP or ABTS with in-situ regeneration of the redox mediator by laccase. As shown in Fig 1, CDH is reduced. When lactose is oxidized to lactobionic acid, in turn, the reduced CDH is re-oxidized with the help of a redox mediator, which is then regenerated through oxidation by laccase. Lastly, laccase is regenerated when the electrons are passed to oxygen, the final electron acceptor. Such a bi-enzyme cascade system was found to be able to drastically boost the rate of conversion of lactose to LBA using ABTS as a redox mediator [12,15].


Production of cellobionate from cellulose using an engineered Neurospora crassa strain with laccase and redox mediator addition.

Hildebrand A, Kasuga T, Fan Z - PLoS ONE (2015)

Enzymatic oxidation of substrate (cellobiose/lactose) by CDH.The reduced CDH is oxidized by a redox mediator (ABTS), which is in turn oxidized by laccase. The reduced laccase is oxidized by oxygen, with water as the only byproduct.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4388835&req=5

pone.0123006.g001: Enzymatic oxidation of substrate (cellobiose/lactose) by CDH.The reduced CDH is oxidized by a redox mediator (ABTS), which is in turn oxidized by laccase. The reduced laccase is oxidized by oxygen, with water as the only byproduct.
Mentions: Baminger et al. reported a novel CDH-ABTS-laccase bi-enzyme system for fast oxidation of lactose to LBA [12]. Laccases are important multicopper oxidases which are also widely distributed in wood degrading fungi [13]. They are especially prevalent in white rot and brown rot fungi, with speculative involvement in lignin degradation [14]. In contrast to CDH, laccases oxidize a large number of reduced substances and use oxygen as the final electron acceptor very efficiently. One strategy to increase the rate of lactose oxidation by CDH with oxygen as the final electron acceptor is to employ catalytic amounts of DCPIP or ABTS with in-situ regeneration of the redox mediator by laccase. As shown in Fig 1, CDH is reduced. When lactose is oxidized to lactobionic acid, in turn, the reduced CDH is re-oxidized with the help of a redox mediator, which is then regenerated through oxidation by laccase. Lastly, laccase is regenerated when the electrons are passed to oxygen, the final electron acceptor. Such a bi-enzyme cascade system was found to be able to drastically boost the rate of conversion of lactose to LBA using ABTS as a redox mediator [12,15].

Bottom Line: By adding low concentrations of laccase and a redox mediator to the fermentation, CDH can be efficiently oxidized by the redox mediator, with in-situ re-oxidation of the redox mediator by laccase.The conversion of cellulose to cellobionate was optimized by evaluating pH, buffer, and laccase and redox mediator addition time on the yield of cellobionate.This paper describes a working concept of cellobionate production from cellulose using the CDH-ATBS-laccase system in a fermentation system.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Agricultural Engineering, University of California, Davis, One Shields Avenue, Davis, CA, 95616, United States of America.

ABSTRACT
We report a novel production process for cellobionic acid from cellulose using an engineered fungal strain with the exogenous addition of laccase and a redox mediator. A previously engineered strain of Neurospora crassa (F5∆ace-1∆cre-1∆ndvB) was shown to produce cellobionate directly from cellulose without the addition of exogenous cellulases. Specifically, N. crassa produces cellulases, which hydrolyze cellulose to cellobiose, and cellobiose dehydrogenase (CDH), which oxidizes cellobiose to cellobionate. However, the conversion of cellobiose to cellobionate is limited by the slow re-oxidation of CDH by molecular oxygen. By adding low concentrations of laccase and a redox mediator to the fermentation, CDH can be efficiently oxidized by the redox mediator, with in-situ re-oxidation of the redox mediator by laccase. The conversion of cellulose to cellobionate was optimized by evaluating pH, buffer, and laccase and redox mediator addition time on the yield of cellobionate. Mass and material balances were performed, and the use of the native N. crassa laccase in such a conversion system was evaluated against the exogenous Pleurotus ostreatus laccase. This paper describes a working concept of cellobionate production from cellulose using the CDH-ATBS-laccase system in a fermentation system.

No MeSH data available.


Related in: MedlinePlus