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Enhancement of Cellulose Degradation by Cattle Saliva.

Seki Y, Kikuchi Y, Kimura Y, Yoshimoto R, Takahashi M, Aburai K, Kanai Y, Ruike T, Iwabata K, Sugawara F, Sakai H, Abe M, Sakaguchi K - PLoS ONE (2015)

Bottom Line: Although cattle saliva, by itself, did not degrade cellulose, it enhanced the cellulase-catalyzed degradation of cellulose.Thus, the amount of reducing sugar produced increased approximately 2.9-fold by the addition of cattle saliva.We also found that non-enzymatic proteins, which were present in cattle saliva, were responsible for causing the enhancement effect.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Science and Technology, Tokyo University of Science, Noda, Chiba, Japan.

ABSTRACT
Saccharification of cellulose is a promising technique for producing alternative source of energy. However, the efficiency of conversion of cellulose into soluble sugar using any currently available methodology is too low for industrial application. Many additives, such as surfactants, have been shown to enhance the efficiency of cellulose-to-sugar conversion. In this study, we have examined first whether cattle saliva, as an additive, would enhance the cellulase-catalyzed hydrolysis of cellulose, and subsequently elucidated the mechanism by which cattle saliva enhanced this conversion. Although cattle saliva, by itself, did not degrade cellulose, it enhanced the cellulase-catalyzed degradation of cellulose. Thus, the amount of reducing sugar produced increased approximately 2.9-fold by the addition of cattle saliva. We also found that non-enzymatic proteins, which were present in cattle saliva, were responsible for causing the enhancement effect. Third, the mechanism of cattle saliva mediated enhancement of cellulase activity was probably similar to that of the canonical surfactants. Cattle saliva is available in large amounts easily and cheaply, and it can be used without further purification. Thus, cattle saliva could be a promising additive for efficient saccharification of cellulose on an industrial scale.

No MeSH data available.


Comparison and competition between cattle saliva and canonical additives.(a) Comparison between the enhancing effects of cattle saliva and canonical additives. The amount of reducing glucose produced was measured using optimal concentration one of the following additives: PEG 4000 (50 mg/mL), Tween 20 (2.5 mg/mL) BSA (0.01 mg/mL), cattle saliva (7.75%) or none. (b) Competition between cattle saliva and Tween 20. Concentrations of cattle saliva and Tween 20 required for saturating the cellulase catalyzed production of reducing sugar were 7.75% and 2.5 mg/mL, respectively. All experiments were performed in triplicate and error bars indicate ± standard deviations. Values labeled with asterisk are statistically different as established by Student's t-test (P < 0.05).
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pone.0138902.g009: Comparison and competition between cattle saliva and canonical additives.(a) Comparison between the enhancing effects of cattle saliva and canonical additives. The amount of reducing glucose produced was measured using optimal concentration one of the following additives: PEG 4000 (50 mg/mL), Tween 20 (2.5 mg/mL) BSA (0.01 mg/mL), cattle saliva (7.75%) or none. (b) Competition between cattle saliva and Tween 20. Concentrations of cattle saliva and Tween 20 required for saturating the cellulase catalyzed production of reducing sugar were 7.75% and 2.5 mg/mL, respectively. All experiments were performed in triplicate and error bars indicate ± standard deviations. Values labeled with asterisk are statistically different as established by Student's t-test (P < 0.05).

Mentions: Several previous studies reported that many different types of additives enhanced the degradation of cellulose. For example, cellulase-catalyzed degradation of cellulose was enhanced by the addition of PEG 4000 [8, 20], Tween 20 [10, 21] or BSA [11, 22]. Therefore, we next confirmed that these three additives indeed enhanced cellulose degradation. First, using various concentrations of PEG 4000 (2.5, 12.5, 25, and 50 mg/mL), we measured the amount of reducing sugar produced, the maximum concentration of which was found to be 0.126 mg/mL at 50 mg/mL of PEG 4000. Second, using various concentrations of Tween 20 (2.5, 12.5, 25, and 50 mg/mL), we measured the amount of reducing sugar produced, the maximum concentration of which was found to be 0.258 mg/mL at 2.5 mg/mL of Tween 20. Third, using various concentrations of BSA (0.005, 0.01, 0.05, 0.1,and 0.5 mg/mL), we measured the amount of sugar produced, the maximum concentration of which was found to be 0.226 mg/mL at 0.01 mg/mL of BSA. These maximum sugar concentration values were plotted again in Fig 9A. As can be seen, the production of reducing sugar was increased 7.5-fold by the addition of PEG 4000, and more than 13.5-fold by the addition of Tween 20, BSA or cattle saliva. These results confirmed the earlier reported observation that the enzymatic activity of cellulase was enhanced by certain types of polymers, proteins and surfactants. In order to further understand the underlying mechanism of the enhancement effect of cattle saliva, we next examined whether cattle saliva could compete with Tween 20. Results of the competition assay were shown in Fig 9B. Since the amount of reducing sugar produced became saturated when we used more than 4% of cattle saliva (Fig 1D) or 2.5 mg/mL of Tween 20 (Fig 9A) as additives, we therefore used 7.75% cattle saliva and 2.5 mg/mL Tween 20 as additives for the competition assay. As shown in Fig 9B, the amount of reducing sugar produced with saliva, Tween 20 and saliva + Tween 20 were 0.184 mg/mL, 0.186 mg/mL and 0.201 mg/mL, respectively. The amount of reducing sugar produced with saliva + Tween 20 was not significantly different compared to that with Tween 20, but was slightly different from that with saliva. The produced sugar rate using saliva was 92% based on using saliva + Tween 20, although saliva + Tween 20 mixture additionally contained Tween 20 compared with saliva mixture. This slight difference was not important to discussing the result of competition assay. Thus, cattle saliva was able to compete with Tween 20 for exerting its enhancing effect. This result suggested that the enhancement effect of cattle saliva possibly mediated via a mechanism that is similar to that of Tween 20. Proteins are composed of various types of hydrophobic and hydrophilic amino acid residues. Thus, just as in surfactants, proteins also have hydrophobic and hydrophilic parts and hence they may behave like surfactants.


Enhancement of Cellulose Degradation by Cattle Saliva.

Seki Y, Kikuchi Y, Kimura Y, Yoshimoto R, Takahashi M, Aburai K, Kanai Y, Ruike T, Iwabata K, Sugawara F, Sakai H, Abe M, Sakaguchi K - PLoS ONE (2015)

Comparison and competition between cattle saliva and canonical additives.(a) Comparison between the enhancing effects of cattle saliva and canonical additives. The amount of reducing glucose produced was measured using optimal concentration one of the following additives: PEG 4000 (50 mg/mL), Tween 20 (2.5 mg/mL) BSA (0.01 mg/mL), cattle saliva (7.75%) or none. (b) Competition between cattle saliva and Tween 20. Concentrations of cattle saliva and Tween 20 required for saturating the cellulase catalyzed production of reducing sugar were 7.75% and 2.5 mg/mL, respectively. All experiments were performed in triplicate and error bars indicate ± standard deviations. Values labeled with asterisk are statistically different as established by Student's t-test (P < 0.05).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4581621&req=5

pone.0138902.g009: Comparison and competition between cattle saliva and canonical additives.(a) Comparison between the enhancing effects of cattle saliva and canonical additives. The amount of reducing glucose produced was measured using optimal concentration one of the following additives: PEG 4000 (50 mg/mL), Tween 20 (2.5 mg/mL) BSA (0.01 mg/mL), cattle saliva (7.75%) or none. (b) Competition between cattle saliva and Tween 20. Concentrations of cattle saliva and Tween 20 required for saturating the cellulase catalyzed production of reducing sugar were 7.75% and 2.5 mg/mL, respectively. All experiments were performed in triplicate and error bars indicate ± standard deviations. Values labeled with asterisk are statistically different as established by Student's t-test (P < 0.05).
Mentions: Several previous studies reported that many different types of additives enhanced the degradation of cellulose. For example, cellulase-catalyzed degradation of cellulose was enhanced by the addition of PEG 4000 [8, 20], Tween 20 [10, 21] or BSA [11, 22]. Therefore, we next confirmed that these three additives indeed enhanced cellulose degradation. First, using various concentrations of PEG 4000 (2.5, 12.5, 25, and 50 mg/mL), we measured the amount of reducing sugar produced, the maximum concentration of which was found to be 0.126 mg/mL at 50 mg/mL of PEG 4000. Second, using various concentrations of Tween 20 (2.5, 12.5, 25, and 50 mg/mL), we measured the amount of reducing sugar produced, the maximum concentration of which was found to be 0.258 mg/mL at 2.5 mg/mL of Tween 20. Third, using various concentrations of BSA (0.005, 0.01, 0.05, 0.1,and 0.5 mg/mL), we measured the amount of sugar produced, the maximum concentration of which was found to be 0.226 mg/mL at 0.01 mg/mL of BSA. These maximum sugar concentration values were plotted again in Fig 9A. As can be seen, the production of reducing sugar was increased 7.5-fold by the addition of PEG 4000, and more than 13.5-fold by the addition of Tween 20, BSA or cattle saliva. These results confirmed the earlier reported observation that the enzymatic activity of cellulase was enhanced by certain types of polymers, proteins and surfactants. In order to further understand the underlying mechanism of the enhancement effect of cattle saliva, we next examined whether cattle saliva could compete with Tween 20. Results of the competition assay were shown in Fig 9B. Since the amount of reducing sugar produced became saturated when we used more than 4% of cattle saliva (Fig 1D) or 2.5 mg/mL of Tween 20 (Fig 9A) as additives, we therefore used 7.75% cattle saliva and 2.5 mg/mL Tween 20 as additives for the competition assay. As shown in Fig 9B, the amount of reducing sugar produced with saliva, Tween 20 and saliva + Tween 20 were 0.184 mg/mL, 0.186 mg/mL and 0.201 mg/mL, respectively. The amount of reducing sugar produced with saliva + Tween 20 was not significantly different compared to that with Tween 20, but was slightly different from that with saliva. The produced sugar rate using saliva was 92% based on using saliva + Tween 20, although saliva + Tween 20 mixture additionally contained Tween 20 compared with saliva mixture. This slight difference was not important to discussing the result of competition assay. Thus, cattle saliva was able to compete with Tween 20 for exerting its enhancing effect. This result suggested that the enhancement effect of cattle saliva possibly mediated via a mechanism that is similar to that of Tween 20. Proteins are composed of various types of hydrophobic and hydrophilic amino acid residues. Thus, just as in surfactants, proteins also have hydrophobic and hydrophilic parts and hence they may behave like surfactants.

Bottom Line: Although cattle saliva, by itself, did not degrade cellulose, it enhanced the cellulase-catalyzed degradation of cellulose.Thus, the amount of reducing sugar produced increased approximately 2.9-fold by the addition of cattle saliva.We also found that non-enzymatic proteins, which were present in cattle saliva, were responsible for causing the enhancement effect.

View Article: PubMed Central - PubMed

Affiliation: Research Institute for Science and Technology, Tokyo University of Science, Noda, Chiba, Japan.

ABSTRACT
Saccharification of cellulose is a promising technique for producing alternative source of energy. However, the efficiency of conversion of cellulose into soluble sugar using any currently available methodology is too low for industrial application. Many additives, such as surfactants, have been shown to enhance the efficiency of cellulose-to-sugar conversion. In this study, we have examined first whether cattle saliva, as an additive, would enhance the cellulase-catalyzed hydrolysis of cellulose, and subsequently elucidated the mechanism by which cattle saliva enhanced this conversion. Although cattle saliva, by itself, did not degrade cellulose, it enhanced the cellulase-catalyzed degradation of cellulose. Thus, the amount of reducing sugar produced increased approximately 2.9-fold by the addition of cattle saliva. We also found that non-enzymatic proteins, which were present in cattle saliva, were responsible for causing the enhancement effect. Third, the mechanism of cattle saliva mediated enhancement of cellulase activity was probably similar to that of the canonical surfactants. Cattle saliva is available in large amounts easily and cheaply, and it can be used without further purification. Thus, cattle saliva could be a promising additive for efficient saccharification of cellulose on an industrial scale.

No MeSH data available.