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The anionic biosurfactant rhamnolipid does not denature industrial enzymes.

Madsen JK, Pihl R, Møller AH, Madsen AT, Otzen DE, Andersen KK - Front Microbiol (2015)

Bottom Line: It efficiently unfolds both LT and CZ, but LT is unfolded by SDS through formation of SDS clusters on the enzyme well below the cmc, while CZ is only unfolded by bulk micelles and on average binds significantly less SDS than LT.In contrast, RL does not affect the tertiary or secondary structure of any enzyme at room temperature, has little impact on thermal stability and only binds detectably (but at low stoichiometries) to SZ.Furthermore, all enzymes maintain activity at both monomeric and micellar concentrations of RL.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University Aarhus, Denmark.

ABSTRACT
Biosurfactants (BS) are surface-active molecules produced by microorganisms. Their combination of useful properties and sustainable production make them promising industrial alternatives to petrochemical and oleochemical surfactants. Here we compare the impact of the anionic BS rhamnolipid (RL) and the conventional/synthetic anionic surfactant sodium dodecyl sulfate (SDS) on the structure and stability of three different commercially used enzymes, namely the cellulase Carezyme® (CZ), the phospholipase Lecitase Ultra® (LT) and the α-amylase Stainzyme® (SZ). Our data reveal a fundamental difference in their mode of interaction. SDS shows great diversity of interaction toward the different enzymes. It efficiently unfolds both LT and CZ, but LT is unfolded by SDS through formation of SDS clusters on the enzyme well below the cmc, while CZ is only unfolded by bulk micelles and on average binds significantly less SDS than LT. SDS binds with even lower stoichiometry to SZ and leads to an increase in thermal stability. In contrast, RL does not affect the tertiary or secondary structure of any enzyme at room temperature, has little impact on thermal stability and only binds detectably (but at low stoichiometries) to SZ. Furthermore, all enzymes maintain activity at both monomeric and micellar concentrations of RL. We conclude that RL, despite its anionic charge, is a surfactant that does not compromise the structural integrity of industrially relevant enzymes. This makes RL a promising alternative to current synthetic anionic surfactants in a wide range of commercial applications.

No MeSH data available.


Change in (A,B) secondary and (C,D) tertiary structure of CZ with increasing surfactant concentration. (A) Far-UV and (C) near-UV CD spectra of CZ in buffer and in the presence of surfactants. Spectra of CZ in buffer and with RL are essentially identical, while SDS induces changes in both secondary and tertiary structure. Changes in the ellipticity at (B) 220 nm and (D) 291 nm reveal a structural change around 2 mM SDS. This coincides with the formation of micelles in the bulk phase.
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Figure 2: Change in (A,B) secondary and (C,D) tertiary structure of CZ with increasing surfactant concentration. (A) Far-UV and (C) near-UV CD spectra of CZ in buffer and in the presence of surfactants. Spectra of CZ in buffer and with RL are essentially identical, while SDS induces changes in both secondary and tertiary structure. Changes in the ellipticity at (B) 220 nm and (D) 291 nm reveal a structural change around 2 mM SDS. This coincides with the formation of micelles in the bulk phase.

Mentions: Far-UV CD spectra of CZ in buffer show a local minimum and maximum at 230 and 220 nm, respectively (Figure 2A). Titration with RL did not lead to any change in the spectra indicating that neither monomeric or micellar RL denature CZ. In contrast, super-cmc SDS concentrations led to large spectral change; plotting ellipticity at 220 nm as a function of SDS show that the change in secondary structure occurs around the cmc (Figure 2B). These conclusions were reinforced by near-UV CD spectra (Figure 2C). Titration of CZ with RL did not lead to any change in spectra while titration with SDS led to disappearance of the two local maxima at ~285 and 295 nm around the cmc region (Figure 2D). Thus, CZ is only denatured by SDS micelles formed in the bulk phase.


The anionic biosurfactant rhamnolipid does not denature industrial enzymes.

Madsen JK, Pihl R, Møller AH, Madsen AT, Otzen DE, Andersen KK - Front Microbiol (2015)

Change in (A,B) secondary and (C,D) tertiary structure of CZ with increasing surfactant concentration. (A) Far-UV and (C) near-UV CD spectra of CZ in buffer and in the presence of surfactants. Spectra of CZ in buffer and with RL are essentially identical, while SDS induces changes in both secondary and tertiary structure. Changes in the ellipticity at (B) 220 nm and (D) 291 nm reveal a structural change around 2 mM SDS. This coincides with the formation of micelles in the bulk phase.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400916&req=5

Figure 2: Change in (A,B) secondary and (C,D) tertiary structure of CZ with increasing surfactant concentration. (A) Far-UV and (C) near-UV CD spectra of CZ in buffer and in the presence of surfactants. Spectra of CZ in buffer and with RL are essentially identical, while SDS induces changes in both secondary and tertiary structure. Changes in the ellipticity at (B) 220 nm and (D) 291 nm reveal a structural change around 2 mM SDS. This coincides with the formation of micelles in the bulk phase.
Mentions: Far-UV CD spectra of CZ in buffer show a local minimum and maximum at 230 and 220 nm, respectively (Figure 2A). Titration with RL did not lead to any change in the spectra indicating that neither monomeric or micellar RL denature CZ. In contrast, super-cmc SDS concentrations led to large spectral change; plotting ellipticity at 220 nm as a function of SDS show that the change in secondary structure occurs around the cmc (Figure 2B). These conclusions were reinforced by near-UV CD spectra (Figure 2C). Titration of CZ with RL did not lead to any change in spectra while titration with SDS led to disappearance of the two local maxima at ~285 and 295 nm around the cmc region (Figure 2D). Thus, CZ is only denatured by SDS micelles formed in the bulk phase.

Bottom Line: It efficiently unfolds both LT and CZ, but LT is unfolded by SDS through formation of SDS clusters on the enzyme well below the cmc, while CZ is only unfolded by bulk micelles and on average binds significantly less SDS than LT.In contrast, RL does not affect the tertiary or secondary structure of any enzyme at room temperature, has little impact on thermal stability and only binds detectably (but at low stoichiometries) to SZ.Furthermore, all enzymes maintain activity at both monomeric and micellar concentrations of RL.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology and Genetics, Aarhus University Aarhus, Denmark.

ABSTRACT
Biosurfactants (BS) are surface-active molecules produced by microorganisms. Their combination of useful properties and sustainable production make them promising industrial alternatives to petrochemical and oleochemical surfactants. Here we compare the impact of the anionic BS rhamnolipid (RL) and the conventional/synthetic anionic surfactant sodium dodecyl sulfate (SDS) on the structure and stability of three different commercially used enzymes, namely the cellulase Carezyme® (CZ), the phospholipase Lecitase Ultra® (LT) and the α-amylase Stainzyme® (SZ). Our data reveal a fundamental difference in their mode of interaction. SDS shows great diversity of interaction toward the different enzymes. It efficiently unfolds both LT and CZ, but LT is unfolded by SDS through formation of SDS clusters on the enzyme well below the cmc, while CZ is only unfolded by bulk micelles and on average binds significantly less SDS than LT. SDS binds with even lower stoichiometry to SZ and leads to an increase in thermal stability. In contrast, RL does not affect the tertiary or secondary structure of any enzyme at room temperature, has little impact on thermal stability and only binds detectably (but at low stoichiometries) to SZ. Furthermore, all enzymes maintain activity at both monomeric and micellar concentrations of RL. We conclude that RL, despite its anionic charge, is a surfactant that does not compromise the structural integrity of industrially relevant enzymes. This makes RL a promising alternative to current synthetic anionic surfactants in a wide range of commercial applications.

No MeSH data available.