Fusion of cellulose binding domain from Trichoderma reesei CBHI to Cryptococcus sp. S-2 cellulase enhances its binding affinity and its cellulolytic activity to insoluble cellulosic substrates

Enhancement of catalytic activity and alkaline stability of cellobiohydrolase by structure-based protein engineering

Alkaline cellobiohydrolases have the potential for application in various industries, including pulp processing and laundry where operation under high pH conditions is preferred. In this study, variants of CtCel6A cellobiohydrolase from Chaetomium thermophilum were generated by structural-based protein engineering with the rationale of increasing catalytic activity and alkaline stability. The variants included removal of the carbohydrate-binding module (CBM) and substitution of residues 173 and 200. The CBM-deleted enzyme with Y200F mutation predicted to mediate conformational change at the N-terminal loop demonstrated increased alkaline stability at 60 °C, pH 8.0 for 24 h up to 2.25-fold compared with the wild-type enzyme. Another CBM-deleted enzyme with L173E mutation predicted to induce a new hydrogen bond in the substrate-binding cleft showed enhanced hydrolysis yield of pretreated sugarcane trash up to 4.65-fold greater than that of the wild-type enzyme at the pH 8.0. The variant enzymes could thus be developed for applications on cellulose hydrolysis and plant fiber modification operated under alkaline conditions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03339-4.

Engineering of a chitosanase fused to a carbohydrate-binding module for continuous production of desirable chitooligosaccharides

Chitooligosaccharides (CHOS) with multiple biological activities are usually produced through enzymatic hydrolysis of chitosan or chitin. However, purification and recycling of the enzyme have largely limited the advancement of CHOS bioproduction. Here, we engineered a novel enzyme by fusing the native chitosanase Csn75 with a carbohydrate-binding module (CBM) that can specifically bind to curdlan. The recombinase Csn75-CBM was successfully expressed by Pichia pastoris and allowed one-step purification and immobilization in the chitosanase immobilized curdlan packed-bed reactor (CICPR), where a maximum adsorption capacity of 39.59 mg enzyme/g curdlan was achieved. CHOS with degrees of polymerization of 2-5 (a hydrolysis yield of 97.75%), 3-6 (75.45%), and 3-7 (73.2%) were continuously produced by adjusting the ratio of enzyme and chitosan or the flow rate of chitosan. Moreover, the CICPR exhibited good stability and reusability after several cycles. The recombinase Csn75-CBM has greatly improved the efficiency of the bioproduction of CHOS.

Effect of carbohydrate binding modules alterations on catalytic activity of glycoside hydrolase family 6 exoglucanase from Chaetomium thermophilum to cellulose

Exoglucanase (CBH) is the rate limiting enzyme in the process of cellulose degradation. The carbohydrate binding module (CBM) can improve the accessibility of cellulase to substrate, thereby promoting the enzymatic hydrolysis of cellulase. In this study, the influence of CBM on the properties of GH6 exoglucanase from Chaetomium thermophilum (CtCBH) is systematically explored from three perspectives: the fusion of exogenous CBM, the exogenous CBM replacement of its own CBM, and the deletion of its own CBM. The parental and reconstructed CtCBH presented the same optimum pH (6.0) and temperature (60 °C) for maximum activity. Fusion of exogenous CBM increased the binding capacity of CtCBH to Avicel by 8% and 9%, respectively, but it had no significant effect on its catalytic activity. The exogenous CBM replacement of its own CBM resulted in a 12% reduction in the binding ability of CtCBH to Avicel, and a 26% reduction in the catalytic activity of Avicel. The deletion of its own CBM significantly reduced the binding ability of CtCBH to Avicel by approximately 53%, but its catalytic activity was not obviously reduced. These observations suggest that binding ability of CBM is not necessary for the catalysis of CtCBH.

Production of beta-galactosidase fused to a cellulose-binding domain for application in sustainable industrial processes

This study aimed to produce and characterize a recombinant Kluyveromyces sp. β-galactosidase fused to a cellulose-binding domain (CBD) for industrial application. In expression assays, the highest enzymatic activities occurred after 48 h induction on Escherichia coli C41(DE3) strain at 20 °C in Terrific Broth (TB) culture medium, using isopropyl β-d-1-thiogalactopyranoside (IPTG) 0.5 mM (108.77 U/mL) or lactose 5 g/L (93.10 U/mL) as inducers. Cultures at bioreactor scale indicated that higher product yield values in relation to biomass (2000 U/g) and productivity (0.72 U/mL.h) were obtained in culture media containing higher protein concentration. The recombinant enzyme showed high binding affinity to nanocellulose, reaching both immobilization yield and efficiency values of approximately 70% at pH 7.0 after 10 min reaction. The results of the present study pointed out a strategy for recombinant β-galactosidase-CBD production and immobilization, aiming toward the application in sustainable industrial processes using low-cost inputs.

Enhanced Thermostability and Enzymatic Activity of Cel6A Variants from Thermobifida fusca by Empirical Domain Engineering (Short Title: Domain Engineering of Cel6A)

Cellulases are a set of lignocellulolytic enzymes, capable of producing eco-friendly low-cost renewable bioethanol. However, low stability and hydrolytic activity limit their wide-scale applicability at the industrial scale. In this work, we report the domain engineering of endoglucanase (Cel6A) of Thermobifida fusca to improve their catalytic activity and thermal stability. Later, enzymatic activity and thermostability of the most efficient variant named as Cel6A.CBC was analyzed by molecular dynamics simulations. This variant demonstrated profound activity against soluble and insoluble cellulosic substrates like filter paper, alkali-treated bagasse, regenerated amorphous cellulose (RAC), and bacterial microcrystalline cellulose. The variant Cel6A.CBC showed the highest catalysis of carboxymethyl cellulose (CMC) and other related insoluble substrates at a pH of 6.0 and a temperature of 60 °C. Furthermore, a sound rationale was observed between experimental findings and molecular modeling of Cel6A.CBC which revealed thermostability of Cel6A.CBC at 26.85, 60.85, and 74.85 °C as well as structural flexibility at 126.85 °C. Therefore, a thermostable derivative of Cel6A engineered in the present work has enhanced biological performance and can be a useful construct for the mass production of bioethanol from plant biomass.

Association between dipsacus saponin VI level and diversity of endophytic fungi in roots of Dipsacus asperoides

Dipsacus asperoides contains multiple pharmacologically active compounds. The principal are saponins. The plant can be cultivated, but it contains lower levels of bioactive compounds than the plant in the wild. It may be the reason to exploit the endophytic fungi that colonize the plant roots in order to produce bioactive compounds. However, the endophytic fungi of D. asperoides have not been analyzed in detail. In this study, we isolated and identified 46 endophytic fungal strains from the taproots, lateral roots and leaves, and we used morphological and molecular biological methods to assign them into 15 genera: Fusarium sp., Ceratobasidium sp., Chaetomium sp., Penicillium sp., Aspergillus sp., Talaromyces sp., Cladosporium sp., Bionectria sp., Mucor sp., Trichoderma sp., Myrothecium sp., Clonostachys sp., Ijuhya sp., Leptosphaeria sp. and Phoma sp. Taproots contained abundant endophytic fungi, the numbers of which correlated positively with level of dipsacus saponin VI. Primary fermentation of several endophytic fungal strains from taproots showed that Fusarium, Leptosphaeria, Ceratobasidium sp. and Phoma sp. can produce the triterpenoid saponin. These results may guide efforts to sustainably produce bioactive compounds from D. asperoides.

Engineered microbial host selection for value-added bioproducts from lignocellulose

Lignocellulose is a rich and sustainable globally available carbon source and is considered a prominent alternative raw material for producing biofuels and valuable chemical compounds. Enzymatic hydrolysis is one of the crucial steps of lignocellulose degradation. Cellulolytic and hemicellulolytic enzyme mixes produced by different microorganisms including filamentous fungi, yeasts and bacteria, are used to degrade the biomass to liberate monosaccharides and other compounds for fermentation or conversion to value-added products. During biomass pretreatment and degradation, toxic compounds are produced, and undesirable carbon catabolic repression (CCR) can occur. In order to solve this problem, microbial metabolic pathways and transcription factors involved have been investigated along with the application of protein engineering to optimize the biorefinery platform. Engineered Microorganisms have been used to produce specific enzymes to breakdown biomass polymers and metabolize sugars to produce ethanol as well other biochemical compounds. Protein engineering strategies have been used for modifying lignocellulolytic enzymes to overcome enzymatic limitations and improving both their production and functionality. Furthermore, promoters and transcription factors, which are key proteins in this process, are modified to promote microbial gene expression that allows a maximum performance of the hydrolytic enzymes for lignocellulosic degradation. The present review will present a critical discussion and highlight the aspects of the use of microorganisms to convert lignocellulose into value-added bioproduct as well combat the bottlenecks to make the biorefinery platform from lignocellulose attractive to the market.

Targeting microplastic particles in the void of diluted suspensions

Accumulation of microplastic in the environment and food chain will be a grand challenge for our society. Polyurethanes are widely used synthetic polymers in medical (e.g. catheters) and industrial products (especially as foams). Polyurethane is not abundant in nature and only a few microbial strains (fungi and bacteria) and enzymes (polyurethaneases and cutinases) have been reported to efficiently degrade polyurethane. Notably, in nature a long period of time (from 50 to >100 years depending on the literature) is required for degradation of plastics. Material binding peptides (e.g. anchor peptides) bind strongly to polymers such as polypropylene, polyethylene terephthalate, and polyurethane and can target specifically polymers. In this study we report the fusion of the anchor peptide Tachystatin A2 to the bacterial cutinase Tcur1278 which accelerated the degradation of polyester-polyurethane nanoparticles by a factor of 6.6 in comparison to wild-type Tcur1278. Additionally, degradation half-lives of polyester-polyurethane nanoparticles were reduced from 41.8 h to 6.2 h (6.7-fold) in a diluted polyester-polyurethane suspension (0.04% w/v).

Construction of Novel Aspartokinase Mutant A380I and Its Characterization by Molecular Dynamics Simulation

In this study, a novel monomer aspartokinase (AK) from Corynebacterium pekinense was identified, and its monomer model was constructed. Site 380 was identified by homologous sequencing and monomer model comparison as the key site which was conserved and located around the binding site of the inhibitor Lys. Furthermore, the mutant A380I with enzyme activity 11.32-fold higher than wild type AK (WT-AK), was obtained by site-directed mutagenesis and high throughput screening. In the mutant A380I, the optimal temperature was raised from 26 °C (WT-AK) to 28 °C, the optimal pH remained unchanged at 8.0, and the half-life was prolonged from 4.5 h (WT-AK) to 6.0 h, indicating enhanced thermal stability. The inhibition of A380I was weakened at various inhibitor concentrations and even activated at certain inhibitor concentrations (10 mM of Lys, 5 mM or 10 mM of Lys + Thr, 10 mM of Lys + Met, 5 mM of Lys + Thr + Met). Molecular dynamics simulation results indicated that the occupancy rate of hydrogen bond between A380I and ATP was enhanced, the effect of Lys (inhibitor) on the protein was weakened, and the angle between Ser281-Tyre358 and Asp359-Gly427 was increased after mutation, leading to an open conformation (R-state) that favored the binding of substrate.

Binding and hydrolysis properties of engineered cellobiohydrolases and endoglucanases

Because cellulase was the main enzyme used in bioconversion of lignocellulose, it was a valid way to reduce the hydrolysis cost by increasing the adsorption and hydrolysis efficiency of cellulase. In this study, modified cellobiohydrolases (CBHs) and endoglucanases (EGs) were constructed. Two engineered cellulases CBH-TrCBM^{V27E,P30D,Link1} and EG-TrCBM^{V27E,P30D,Link1} well-performed during hydrolysis. Compared to wild-type enzymes, EG-TrCBM^{V27E,P30D,Link1} had relatively less adsorption ability to lignin and greater affinity to cellulose, especially Avicel. However, for CBH-TrCBM^{V27E,P30D,Link1}, the hydrolysis manner was changed and in favor to hydrolysis process, although the adsorption properties were unexpected. It suggested that various binding conformations of polysaccharide on CBMs hypothetically resulted in different functions of CBMs, including binding ability, processive and digestive properties on fiber surface. Fusion of T. r-CBM^{V27E,P30D,Link1} to cellulase, both CBH and EG, gave the destruction ability of enzyme and increased the accessible surface of substrate to cellulase, enhanced the adsorption and hydrolysis efficiency of cellulase.

The cellulose binding region in Trichoderma reesei cellobiohydrolase I has a higher capacity in improving crystalline cellulose degradation than that of Penicillium oxalicum

Commercial cellulase preparations for lignocellulose bioconversion are mainly produced by the fungus Trichoderma reesei. The maximum cellulose conversion of T. reesei cellulase mixture was 15%-20% higher than that of Penicillium oxalicum in the hydrolysis of corncob residue and Avicel. Nevertheless, both preparations hydrolyzed more than 92% of cellulose in NaOH-mercerized Avicel. When added to Avicel hydrolysis residue that was less reactive to P. oxalicum cellulases, cellobiohydrolase I (CBH I) from T. reesei resulted in a higher cellulose conversion than its homologous proteins from P. oxalicum and Aspergillus niger at the same protein loadings. Further domain exchange experiment attributed the high hydrolytic efficiency of T. reesei CBH I to its inter-domain linker and cellulose-binding domain. The results in part explained the superior performance of T. reesei cellulases on the degradation of native crystalline cellulose, and highlighted the important role of cellulose-binding region in determining the degree of hydrolysis by cellulases.

Carbohydrate-binding module assisted purification and immobilization of β-glucosidase onto cellulose and application in hydrolysis of soybean isoflavone glycosides

Complicated purification steps, together with the fact that β-glucosidase has to be tolerant to ethanol restricts the application of β-glucosidase in isoflavone aglycone hydrolyzing process. β-Glucosidase Bgl1A(A24S/F297Y) is a promising enzyme in hydrolyzing isoflavones. In this work, six different carbohydrate-binding modules (CBMs), which were from 3 families, were fused to the C-terminal of Bgl1A(A24S/F297Y), respectively, to simplify the enzyme preparation process. The fusion proteins were expressed in Escherichia coli and adsorbed onto cellulose. The Bgl-CBM24 was found to have the highest immobilization efficiency at room temperature within 1 h adsorption. Notably, 1-g cellulose absorbs up to 254.9±5.7 U of Bgl-CBM24. Interestingly, the immobilized Bgl-CBM24 showed improved ethanol tolerance ability, with the IC50 of 35% (v/v) ethanol. Bgl-CBM24 effectively hydrolyze soybean isoflavone glycosides. The hydrolysis rate of daidzin and gemistin was 85.22±3.24% and 82.14±3.82% within 10 min, with the concentrations of daidzein and genistein increased by 6.36±0.18 mM and 3.98±0.22 mM, respectively. In the repetitive hydrolytic cycles, the concentrations of daidzein and genistein still increased by 3.07±0.24 mM and 1.94±0.34 mM in the fourth cycle with 20% (v/v) ethanol. These results suggest that the immobilized Bgl-CBM24 has excellent potential in the preparation of isoflavone aglycones.

Light induced expression of β-glucosidase in Escherichia coli with autolysis of cell

Background

β-Glucosidase has attracted substantial attention in the scientific community because of its pivotal role in cellulose degradation, glycoside transformation and many other industrial processes. However, the tedious and costly expression and purification procedures have severely thwarted the industrial applications of β-glucosidase. Thus development of new strategies to express β-glucosidases with cost-effective and simple procedure to meet the increasing demands on enzymes for biocatalysis is of paramount importance.

Results

Light activated cassette YF1/FixJ and the SRRz lysis system were successfully constructed to produce Bgl1A(A24S/F297Y), a mutant β-glucosidase tolerant to both glucose and ethanol. By optimizing the parameters for light induction, Bgl1A(A24S/F297Y) activity reached 33.22 ± 2.0 U/mL and 249.92 ± 12.25 U/mL in 250-mL flask and 3-L fermentation tank, respectively, comparable to the controls of 34.02 ± 1.96 U/mL and 322.21 ± 10.16 U/mL under similar culture conditions with IPTG induction. To further simplify the production of our target protein, the SRRz lysis gene cassette from bacteriophage Lambda was introduced to trigger cell autolysis. As high as 84.53 ± 6.79% and 77.21 ± 4.79% of the total β-glucosidase were released into the lysate after cell autolysis in 250 mL flasks and 3-L scale fermentation with lactose as inducer of SRRz. In order to reduce the cost of protein purification, a cellulose-binding module (CBM) from Clostridium thermocellum was fused into the C-terminal of Bgl1A(A24S/F297Y) and cellulose was used as an economic material to adsorb the fusion enzyme from the lysate. The yield of the fusion protein could reach 92.20 ± 2.27% after one-hour adsorption at 25 °C.

Conclusions

We have developed an efficient and inexpensive way to produce β-glucosidase for potential industrial applications by using the combination of light induction, cell autolysis, and CBM purification strategy.

Electronic supplementary material

The online version of this article (10.1186/s12896-017-0402-1) contains supplementary material, which is available to authorized users.

Impact of Module-X2 and Carbohydrate Binding Module-3 on the catalytic activity of associated glycoside hydrolases towards plant biomass

Cellulolytic enzymes capable of hydrolyzing plant biomass are secreted by microbial cells specifically in response to the carbon substrate present in the environment. These enzymes consist of a catalytic domain, generally appended to one or more non-catalytic Carbohydrate Binding Module (CBM), which enhances their activity towards recalcitrant biomass. In the present study, the genome of a cellulolytic microbe Paenibacillus polymyxa A18 was annotated for the presence of CBMs and analyzed their expression in response to the plant biomass and model polysaccharides Avicel, CMC and xylan using quantitative PCR. A gene that encodes X2-CBM3 was found to be maximally induced in response to the biomass and crystalline substrate Avicel. Association of X2-CBM3 with xyloglucanase and endoglucanase led to up to 4.6-fold increase in activity towards insoluble substrates. In the substrate binding study, module X2 showed a higher affinity towards biomass and phosphoric acid swollen cellulose, whereas CBM3 showed a higher affinity towards Avicel. Further structural modeling of X2 also indicated its potential role in substrate binding. Our findings highlighted the role of module X2 along with CBM3 in assisting the enzyme catalysis of agricultural residue and paved the way to engineer glycoside hydrolases for superior activity.

Cellulases and beyond: the first 70 years of the enzyme producer Trichoderma reesei

More than 70 years ago, the filamentous ascomycete Trichoderma reesei was isolated on the Solomon Islands due to its ability to degrade and thrive on cellulose containing fabrics. This trait that relies on its secreted cellulases is nowadays exploited by several industries. Most prominently in biorefineries which use T. reesei enzymes to saccharify lignocellulose from renewable plant biomass in order to produce biobased fuels and chemicals. In this review we summarize important milestones of the development of T. reesei as the leading production host for biorefinery enzymes, and discuss emerging trends in strain engineering. Trichoderma reesei has very recently also been proposed as a consolidated bioprocessing organism capable of direct conversion of biopolymeric substrates to desired products. We therefore cover this topic by reviewing novel approaches in metabolic engineering of T. reesei.

Subsite-specific contributions of different aromatic residues in the active site architecture of glycoside hydrolase family 12

The active site architecture of glycoside hydrolase (GH) is a contiguous subregion of the enzyme constituted by residues clustered in the three-dimensional space, recognizing the monomeric unit of ligand through hydrogen bonds and hydrophobic interactions. Mutations of the key residues in the active site architecture of the GH12 family exerted different impacts on catalytic efficiency. Binding affinities between the aromatic amino acids and carbohydrate rings were quantitatively determined by isothermal titration calorimetry (ITC) and the quantum mechanical (QM) method, showing that the binding capacity order of Tyr>Trp>His (and Phe) was determined by their side-chain properties. The results also revealed that the binding constant of a certain residue remained unchanged when altering its location, while the catalytic efficiency changed dramatically. Increased binding affinity at a relatively distant subsite, such as the mutant of W7Y at the -4 subsite, resulted in a marked increase in the intermediate product of cellotetraose and enhanced the reactivity of endoglucanase by 144%; while tighter binding near the catalytic center, i.e. W22Y at the -2 subsite, enabled the enzyme to bind and hydrolyze smaller oligosaccharides. Clarification of the specific roles of the aromatics at different subsites may pave the way for a more rational design of GHs.

Earthworms modify microbial community structure and accelerate maize stover decomposition during vermicomposting

In the present study, maize stover was vermicomposted with the epigeic earthworm Eisenia fetida. The results showed that, during vermicomposting process, the earthworms promoted decomposition of maize stover. Analysis of microbial communities of the vermicompost by high-throughput pyrosequencing showed more complex bacterial community structure in the substrate treated by the earthworms than that in the control group. The dominant microbial genera in the treatment with the earthworms were Pseudoxanthomonas, Pseudomonas, Arthrobacter, Streptomyces, Cryptococcus, Guehomyces, and Mucor. Compared to the control group, the relative abundance of lignocellulose degradation microorganisms increased. The results indicated that the earthworms modified the structure of microbial communities during vermicomposting process, activated the growth of lignocellulose degradation microorganisms, and triggered the lignocellulose decomposition.

Recombinant CBM-fusion technology - Applications overview

Carbohydrate-binding modules (CBMs) are small components of several enzymes, which present an independent fold and function, and specific carbohydrate-binding activity. Their major function is to bind the enzyme to the substrate enhancing its catalytic activity, especially in the case of insoluble substrates. The immense diversity of CBMs, together with their unique properties, has long raised their attention for many biotechnological applications. Recombinant DNA technology has been used for cloning and characterizing new CBMs. In addition, it has been employed to improve the purity and availability of many CBMs, but mainly, to construct bi-functional CBM-fused proteins for specific applications. This review presents a comprehensive summary of the uses of CBMs recombinantly produced from heterologous organisms, or by the original host, along with the latest advances. Emphasis is given particularly to the applications of recombinant CBM-fusions in: (a) modification of fibers, (b) production, purification and immobilization of recombinant proteins, (c) functionalization of biomaterials and (d) development of microarrays and probes.

Catalytic efficiency of chitinase-D on insoluble chitinous substrates was improved by fusing auxiliary domains

Chitin is an abundant renewable polysaccharide, next only to cellulose. Chitinases are important for effective utilization of this biopolymer. Chitinase D from Serratia proteamaculans (SpChiD) is a single domain chitinase with both hydrolytic and transglycosylation (TG) activities. SpChiD had less of hydrolytic activity on insoluble polymeric chitin substrates due to the absence of auxiliary binding domains. We improved catalytic efficiency of SpChiD in degradation of insoluble chitin substrates by fusing with auxiliary domains like polycystic kidney disease (PKD) domain and chitin binding protein 21 (CBP21). Of the six different SpChiD fusion chimeras, two C-terminal fusions viz. ChiD+PKD and ChiD+CBP resulted in improved hydrolytic activity on α- and β-chitin, respectively. Time-course degradation of colloidal chitin also confirmed that these two C-terminal SpChiD fusion chimeras were more active than other chimeras. More TG products were produced for a longer duration by the fusion chimeras ChiD+PKD and PKD+ChiD+CBP.

Extra tyrosine in the carbohydrate-binding module of Irpex lacteus Xyn10B enhances its cellulose-binding ability

The xylanase (Xyn10B) that strongly adsorbs on microcrystalline cellulose was isolated from Driselase. The Xyn10B contains a Carbohydrate-binding module family 1 (CBM1) (IrpCBMXyn10B) at N-terminus. The canonical essential aromatic residues required for cellulose binding were conserved in IrpCBMXyn10B; however, its adsorption ability was markedly higher than that typically observed for the CBM1 of an endoglucanase from Trametes hirsuta (ThCBMEG1). An analysis of the CBM-GFP fusion proteins revealed that the binding capacity to cellulose (7.8 μmol/g) and distribution coefficient (2.0 L/μmol) of IrpCBMXyn10B-GFP were twofold higher than those of ThCBMEG1-GFP (3.4 μmol/g and 1.2 L/μmol, respectively), used as a reference structure. Besides the canonical aromatic residues (W24-Y50-Y51) of typical CBM1-containing proteins, IrpCBMXyn10B had an additional aromatic residue (Y52). The mutation of Y52 to Ser (IrpCBMY52S-GFP) reduced these adsorption parameters to 4.4 μmol/g and 1.5 L/μmol, which were similar to those of ThCBMEG1-GFP. These results indicate that Y52 plays a crucial role in strong cellulose binding.

Dissecting the effect of chemical additives on the enzymatic hydrolysis of pretreated wheat straw

Chemical additives were examined for ability to increase the enzymatic hydrolysis of thermo-acidically pretreated wheat straw by Trichoderma reesei cellulase at 50 °C. Semi-empirical descriptors derived from the hydrolysis time courses were applied to compare influence of these additives on lignocellulose bioconversion on a kinetic level, presenting a novel view on their mechanism of action. Focus was on rate retardation during hydrolysis, substrate conversion and enzyme adsorption. PEG 8000 enabled a reduction of enzyme loading by 50% while retaining the same conversion of 67% after 24h. For the first time, a beneficial effect of urea is reported, increasing the final substrate conversion after 48 h by 16%. The cationic surfactant cetyl-trimethylammonium bromide (CTAB) enhanced the hydrolysis rate at extended reaction time (rlim) by 34% and reduced reaction time by 28%. A combination of PEG 8000 and urea increased sugar release more than additives used individually.