Adsorption of Enzymes at Interfaces: Film Formation and the Effect on Activity

James, Laylin K.; Augenstein, Leroy

doi:10.1002/9780470122730.ch1

Cited by 38 publications

(17 citation statements)

References 114 publications

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“…Proteins are known to deactivate at the air-liquid interface to minimize surface excess 44 . They can unfold and expose their hydrophobic groups to the gas phase that were previously buried inside their tertiary structure in bulk aqueous solution.…”

Section: Resultsmentioning

confidence: 99%

“…They can unfold and expose their hydrophobic groups to the gas phase that were previously buried inside their tertiary structure in bulk aqueous solution. Exclusion of hydrophobic regions from the aqueous phase decreases the free energy that drives their adsorption in the interfacial layer 44 , 45 . Because cellulases have a catalytic core and a carbohydrate binding module (CBM) joined together by a linker region 46 , it is possible for hydrophobic platform of CBM that binds to cellulose 47 to orient itself toward the air phase and catalytic core toward the aqueous phase at the air-water interface.…”

Section: Resultsmentioning

confidence: 99%

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Deactivation of Cellulase at the Air-Liquid Interface Is the Main Cause of Incomplete Cellulose Conversion at Low Enzyme Loadings

Bhagia

Dhir

Kumar

et al. 2018

Sci Rep

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Amphiphilic additives such as bovine serum albumin (BSA) and Tween have been used to improve cellulose hydrolysis by cellulases. However, there has been a lack of clarity to explain their mechanism of action in enzymatic hydrolysis of pure or low-lignin cellulosic substrates. In this work, a commercial Trichoderma reesei enzyme preparation and the amphiphilic additives BSA and Tween 20 were applied for hydrolysis of pure Avicel cellulose. The results showed that these additives only had large effects on cellulose conversion at low enzyme to substrate ratios when the reaction flasks were shaken. Furthermore, changes in the air-liquid interfacial area profoundly affected cellulose conversion, but surfactants reduced or prevented cellulase deactivation at the air-liquid interface. Not shaking the flasks or adding low amounts of surfactant resulted in near theoretical cellulose conversion at low enzyme loadings given enough reaction time. At low enzyme loadings, hydrolysis of cellulose in lignocellulosic biomass with low lignin content suffered from enhanced enzyme deactivation at the air-liquid interface.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Deactivation of Cellulase at the Air-Liquid Interface Is the Main Cause of Incomplete Cellulose Conversion at Low Enzyme Loadings

Bhagia

Dhir

Kumar

et al. 2018

Sci Rep

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“…Adsorption of all cellulases at the air–liquid interfaces is unlikely to be the same because differences in their physicochemical properties will affect their air–liquid surface activity. It has been long known that proteins have maximum adsorption at the air–liquid interface at their isoelectric point (pI) [53]. Due to lack of net charge at pI, there is no electric barrier to interfacial adsorption, and proteins may aggregate due to lack of repulsive forces [53].…”

Section: Discussionmentioning

confidence: 99%

“…It has been long known that proteins have maximum adsorption at the air–liquid interface at their isoelectric point (pI) [53]. Due to lack of net charge at pI, there is no electric barrier to interfacial adsorption, and proteins may aggregate due to lack of repulsive forces [53]. Cel7A, Cel6A, Cel7B, and Cel5A have isoelectric points (pI) of 4.5–4.7, 5.0–5.2, 4.6–4.7, and 4.8–5.0, and GRAVY indices (grand average of hydropathy) [54] of − 4.33, − 0.18, − 0.37, and − 0.19 (larger value means protein is more hydrophobic), respectively.…”

Section: Discussionmentioning

confidence: 99%

Impacts of cellulase deactivation at the moving air–liquid interface on cellulose conversions at low enzyme loadings

Bhagia

Wyman

Kumar

2019

Biotechnol Biofuels

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Background We recently confirmed that the deactivation of T. reesei cellulases at the air–liquid interface reduces microcrystalline cellulose conversion at low enzyme loadings in shaken flasks. It is one of the main causes for lowering of cellulose conversions at low enzyme loadings. However, supplementing cellulases with small quantities of surface-active additives in shaken flasks can increase cellulose conversions at low enzyme loadings. It was also shown that cellulose conversions at low enzyme loadings can be increased in unshaken flasks if the reactions are carried for a longer time. This study further explores these recent findings to better understand the impact of air–liquid interfacial phenomena on enzymatic hydrolysis of cellulose contained in Avicel, Sigmacell, α-cellulose, cotton linters, and filter paper. The impacts of solids and enzyme loadings, supplementation with nonionic surfactant Tween 20 and xylanases, and application of different types of mixing and reactor designs on cellulose hydrolysis were also evaluated. Results Avicel cellulose conversions at high solid loading were more than doubled by minimizing loss of cellulases to the air–liquid interface. Maximum cellulose conversions were high for surface-active supplemented shaken flasks or unshaken flasks because of low cellulase deactivation at the air–liquid interface. The nonionic surfactant Tween 20 was unable to completely prevent cellulase deactivation in shaken flasks and only reduced cellulose conversions at unreasonably high concentrations. Conclusions High dynamic interfacial areas created through baffles in reactor vessels, low volumes in high-capacity vessels, or high shaking speeds severely limited cellulose conversions at low enzyme loadings. Precipitation of cellulases due to aggregation at the air–liquid interface caused their continuous deactivation in shaken flasks and severely limited solubilization of cellulose. Electronic supplementary material The online version of this article (10.1186/s13068-019-1439-2) contains supplementary material, which is available to authorized users.

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“…The monolayer technique requires only a small amount of lipid, an advantage when using rare synthetic lipids. A problem with this technique, however, is the denaturation of enzymes that occurs at the lipid-water interface [43,44]. The velocity of lipolysis is dependent on those factors that modify both the physicochemical properties of the interface as well as the surface area [45][46][47].…”

Section: Intestinal Lumenmentioning

confidence: 99%