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Doubling Power Output of Starch Biobattery Treated by the Most Thermostable Isoamylase from an Archaeon Sulfolobus tokodaii.

Cheng K, Zhang F, Sun F, Chen H, Percival Zhang YH - Sci Rep (2015)

Bottom Line: This enzyme was characterized and required Mg(2+) as an activator.This enzyme was the most stable isoamylase reported with a half lifetime of 200 min at 90 (o)C in the presence of 0.5 mM MgCl2, suitable for simultaneous starch gelatinization and isoamylase hydrolysis.The cuvett-based air-breathing biobattery powered by isoamylase-treated starch exhibited nearly doubled power outputs than that powered by the same concentration starch solution, suggesting more glucose 1-phosphate generated.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, Henan Agricultural University, 95 Wenhua Road, Zhengzhou, 450002, China.

ABSTRACT
Biobattery, a kind of enzymatic fuel cells, can convert organic compounds (e.g., glucose, starch) to electricity in a closed system without moving parts. Inspired by natural starch metabolism catalyzed by starch phosphorylase, isoamylase is essential to debranch alpha-1,6-glycosidic bonds of starch, yielding linear amylodextrin - the best fuel for sugar-powered biobattery. However, there is no thermostable isoamylase stable enough for simultaneous starch gelatinization and enzymatic hydrolysis, different from the case of thermostable alpha-amylase. A putative isoamylase gene was mined from megagenomic database. The open reading frame ST0928 from a hyperthermophilic archaeron Sulfolobus tokodaii was cloned and expressed in E. coli. The recombinant protein was easily purified by heat precipitation at 80 (o)C for 30 min. This enzyme was characterized and required Mg(2+) as an activator. This enzyme was the most stable isoamylase reported with a half lifetime of 200 min at 90 (o)C in the presence of 0.5 mM MgCl2, suitable for simultaneous starch gelatinization and isoamylase hydrolysis. The cuvett-based air-breathing biobattery powered by isoamylase-treated starch exhibited nearly doubled power outputs than that powered by the same concentration starch solution, suggesting more glucose 1-phosphate generated.

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Representative polarization and power curves for biobatteries powered by isoamylase-treated starch.(a) and non-treated starch (b). Cyclic voltammetry curves of biobatteries powered by isoamylase-treated starch and non-treated starch (c). Photo of a cuvette-based air-breathing biobattery (d).
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f6: Representative polarization and power curves for biobatteries powered by isoamylase-treated starch.(a) and non-treated starch (b). Cyclic voltammetry curves of biobatteries powered by isoamylase-treated starch and non-treated starch (c). Photo of a cuvette-based air-breathing biobattery (d).

Mentions: A de novo synthetic enzymatic pathway was designed to generate electricity from starch (Fig. 1b). In it, alpha-glucan phosphorylase (αGP) cleaves alpha-1,4-glycosidic bonds from nonreducing ends of starch, maltodextrin or amylodextrin in the presence of phosphate, yielding glucose 1-phosphate; phosphoglucomutase (PGM) converts glucose 6-phosphate; glucose 6-phosphate dehydrogenase generates NADH from glucose 6-phosphate and release 6-phosphogluconate; diaphorase transfers hydrides from NADH via a mediator AQDS to anode. This pathway was slightly different from the previous pathway used28: (i) amylopectin instead of maltodextrin as the substrate, and (ii) non-immobilized AQDS instead of immobilized VK3 as the mediator. The entire sugar biobattery based on a typical plastic cuvette without mobile parts is shown in Fig. 6d. Figure 6 shows the results of electrochemical tests of sugar batteries powered by starch and isoamylase-treated starch. Figure 6a,b display the polarization curves using isoamylase-treated or nontreated starch as the sugar biobattery’s substrate, respectively. When nontreated starch was used, the polarization curve shows that the open circuit potential (OCV) was 0.23 V with short connection current of 0.029 mA. At 0.14 V, the power density reached to a peak of 2.2 μW/cm2. In contrast, feeding the biobattery with isoamylase-treated starch, the maximum power density was almost doubled from 2.2 to 4.1 μW/cm2. In the meantime, short connection current increased to 0.042 mA, and OCV increased to 0.31 V. To eliminate the different cathode performance, individual potentials were recorded (data was not shown). Both of the cathode potentials were 0.53 V with different substrates. Only the anode leaded to varied whole cell performance, suggesting more glucose 1-phosphate generated from isoamylase-treated starch. To further confirm this testing result, cyclic voltammetry were recorded in two types of anolyte solutions. As shown in Fig. 6c, both of the starches showed very slight oxidation peaks which may result from low concentration starch (0.012% wt/v). Both oxidation peaks of isoamylase-treated and nontreated starch were approximately −300 mV relative to Ag/AgCl, but isoamylase-treated starch had higher current indicating isoamylase-treated starch was better than nontreated starch in the anode reaction.


Doubling Power Output of Starch Biobattery Treated by the Most Thermostable Isoamylase from an Archaeon Sulfolobus tokodaii.

Cheng K, Zhang F, Sun F, Chen H, Percival Zhang YH - Sci Rep (2015)

Representative polarization and power curves for biobatteries powered by isoamylase-treated starch.(a) and non-treated starch (b). Cyclic voltammetry curves of biobatteries powered by isoamylase-treated starch and non-treated starch (c). Photo of a cuvette-based air-breathing biobattery (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4542469&req=5

f6: Representative polarization and power curves for biobatteries powered by isoamylase-treated starch.(a) and non-treated starch (b). Cyclic voltammetry curves of biobatteries powered by isoamylase-treated starch and non-treated starch (c). Photo of a cuvette-based air-breathing biobattery (d).
Mentions: A de novo synthetic enzymatic pathway was designed to generate electricity from starch (Fig. 1b). In it, alpha-glucan phosphorylase (αGP) cleaves alpha-1,4-glycosidic bonds from nonreducing ends of starch, maltodextrin or amylodextrin in the presence of phosphate, yielding glucose 1-phosphate; phosphoglucomutase (PGM) converts glucose 6-phosphate; glucose 6-phosphate dehydrogenase generates NADH from glucose 6-phosphate and release 6-phosphogluconate; diaphorase transfers hydrides from NADH via a mediator AQDS to anode. This pathway was slightly different from the previous pathway used28: (i) amylopectin instead of maltodextrin as the substrate, and (ii) non-immobilized AQDS instead of immobilized VK3 as the mediator. The entire sugar biobattery based on a typical plastic cuvette without mobile parts is shown in Fig. 6d. Figure 6 shows the results of electrochemical tests of sugar batteries powered by starch and isoamylase-treated starch. Figure 6a,b display the polarization curves using isoamylase-treated or nontreated starch as the sugar biobattery’s substrate, respectively. When nontreated starch was used, the polarization curve shows that the open circuit potential (OCV) was 0.23 V with short connection current of 0.029 mA. At 0.14 V, the power density reached to a peak of 2.2 μW/cm2. In contrast, feeding the biobattery with isoamylase-treated starch, the maximum power density was almost doubled from 2.2 to 4.1 μW/cm2. In the meantime, short connection current increased to 0.042 mA, and OCV increased to 0.31 V. To eliminate the different cathode performance, individual potentials were recorded (data was not shown). Both of the cathode potentials were 0.53 V with different substrates. Only the anode leaded to varied whole cell performance, suggesting more glucose 1-phosphate generated from isoamylase-treated starch. To further confirm this testing result, cyclic voltammetry were recorded in two types of anolyte solutions. As shown in Fig. 6c, both of the starches showed very slight oxidation peaks which may result from low concentration starch (0.012% wt/v). Both oxidation peaks of isoamylase-treated and nontreated starch were approximately −300 mV relative to Ag/AgCl, but isoamylase-treated starch had higher current indicating isoamylase-treated starch was better than nontreated starch in the anode reaction.

Bottom Line: This enzyme was characterized and required Mg(2+) as an activator.This enzyme was the most stable isoamylase reported with a half lifetime of 200 min at 90 (o)C in the presence of 0.5 mM MgCl2, suitable for simultaneous starch gelatinization and isoamylase hydrolysis.The cuvett-based air-breathing biobattery powered by isoamylase-treated starch exhibited nearly doubled power outputs than that powered by the same concentration starch solution, suggesting more glucose 1-phosphate generated.

View Article: PubMed Central - PubMed

Affiliation: College of Life Sciences, Henan Agricultural University, 95 Wenhua Road, Zhengzhou, 450002, China.

ABSTRACT
Biobattery, a kind of enzymatic fuel cells, can convert organic compounds (e.g., glucose, starch) to electricity in a closed system without moving parts. Inspired by natural starch metabolism catalyzed by starch phosphorylase, isoamylase is essential to debranch alpha-1,6-glycosidic bonds of starch, yielding linear amylodextrin - the best fuel for sugar-powered biobattery. However, there is no thermostable isoamylase stable enough for simultaneous starch gelatinization and enzymatic hydrolysis, different from the case of thermostable alpha-amylase. A putative isoamylase gene was mined from megagenomic database. The open reading frame ST0928 from a hyperthermophilic archaeron Sulfolobus tokodaii was cloned and expressed in E. coli. The recombinant protein was easily purified by heat precipitation at 80 (o)C for 30 min. This enzyme was characterized and required Mg(2+) as an activator. This enzyme was the most stable isoamylase reported with a half lifetime of 200 min at 90 (o)C in the presence of 0.5 mM MgCl2, suitable for simultaneous starch gelatinization and isoamylase hydrolysis. The cuvett-based air-breathing biobattery powered by isoamylase-treated starch exhibited nearly doubled power outputs than that powered by the same concentration starch solution, suggesting more glucose 1-phosphate generated.

No MeSH data available.


Related in: MedlinePlus