Modulation of the activity and selectivity of the immobilized lipases by surfactants and solvents

Most of lipases are in equilibrium between a majority inactive closed form and a minority active open form in aqueous media. Perhaps, a certain stabilization of these open forms of lipases could be achieved in the presence of cosolvents or surfactants in the reaction medium. Three commercial lipases were studied (from Thermomyces lanuginosa (TLL), Candida Antarctica fraction B (CALB) and Lecitase (LEC)). Different derivatives were tested: TLL and LEC were adsorbed on an anionic exchanger and their activity strongly depends on the equilibrium between their open and closed form and CALB was adsorbed on a hydrophobic support when the open form was already stabilized by the support. Derivatives ionically adsorbed were hyperactivated by surfactans as well as by cosolvents: the activity of LEC increased 12 times in the presence of 15-20% of ethanol. CALB adsorbed on hydrophobic supports was hardly hyperactivated and even it was inhibited. The modification of the rate of covalent modification of the catalytic Ser seems to confirm that the observed hyperactivations were due to a stabilization of the open form of the adsorbed lipases (TLL and LEC). The hydrolysis of sardine oil was also studied in the presence or absence of surfactants and cosolvents. An interesting improvement in the ability of derivatives to discriminate the release of eicosipentaenic acid (EPA) and docosahexaenicacid (DHA) was found.The authors thank the financial support of Coordination for the Improvement of Higher Level -or Education Personnel (CAPES) and São Paulo Research Foundation (FAPESP), grant 2013/00530-0.Peer Reviewe

Production of xylo-oligosaccharides by immobilized-stabilized derivatives of endo-xylanase from Streptomyces halstedii

An endoxylanase from Streptomyces halstedii was stabilized by multipoint covalent immobilization on glyoxyl-agarose supports. The immobilized enzyme derivatives preserved 65% of the catalytic activity corresponding to the one of soluble enzyme that had been immobilized. These immobilized derivatives were 200 times more stable 200 times more stable than the one-point covalently immobilized derivative in experiments involving thermal inactivation at 60 °C. The activity and stability of the immobilized enzyme was higher at pH 5.0 than at pH 7.0. The optimal temperature for xylan hydrolysis was 10 °C higher for the stabilized derivative than for the non-stabilized derivative. On the other hand, the highest loading capacity of activated 10% agarose gels was 75 mg of enzyme per mL of support. To prevent diffusional limitations, low loaded derivatives (containing 0.2 mg of enzyme per mL of support) were used to study the hydrolysis of xylan at high concentration (close to 1% (w/v)). 80% of the reducing sugars were released after 3 h at 55 °C. After 80% of enzymatic hydrolysis, a mixture of small xylo-oligosaccharides was obtained (from xylobiose to xylohexose) with a high percentage of xylobiose and minimal amounts of xylose. The immobilized-stabilized derivatives were used for 10 reaction cycles with no loss of catalytic activity. © 2013 Elsevier Ltd. All rights reserved.This work has been supported by the Ministerio de Ciencia e Innovación, Spain (Grant No. EUI2008-03631 from ERA-IB to R. I. Santamaría and Grant AGL-2009-07625 to Jose M. Guisan). Gloria Fernández-Lorente is recipient of a Ramon y Cajal postdoctoral Contract. Caio Aragon thanks Brazilian agencies FAPESP (2008/09332-8) and CAPES (3756/10-6) for financial support.Peer Reviewe

Production of xylo-oligosaccharides (XOS) by controlled hydrolysis of xylan using immobilized xylanase from Aspergillus niger with improved properties

The production of xylo-oligosaccharides from xylan using an optimal immobilized catalyst of xylanase from Aspergillus niger is presented. The enzyme extract has several xylanases with different properties doing necessary the development of cheap and simple methods to purify them at industrial scale. The enzyme was successfully purified, immobilized and highly stabilized using a simple protocol. The principal purified xylanase was a 34 KDa protein corresponding with 50% of the endo-xylanase activity of the total strain. Among the different immobilization assayed protocols, the use of aldehyde support allowed the complete immobilization of this fraction keeping 80% of its initial catalytic activity. An optimization of this method promoted a stabilization factor of around 1100-fold more stable than soluble enzyme. The use of the optimal catalyst allowed a maximum hydrolysis degree of 73.4%. The optimization of the reaction conditions (different time and temperature) allowed producing 62% (11.93 mg/mL) of interesting xylooligo-saccharides (XOS2-XOS6) (Figure 1).Ramón Areces foundation financial support is highly recognized. C.C. Aragon thanks Brazilian agencies FAPESP (2008/09332-8) and CAPES (3756-10-6) for financial support. This work was supported by the Spanish Government (AGL2017-84614-C2-1-R).Peer Reviewe

β-xylosidase from Selenomonas ruminantium: Immobilization, stabilization, and application for xylooligosaccharide hydrolysis

The tetrameric β-xylosidase from Selenomonas ruminantium is very stable in alkaline pH allowing it to easily immobilize by multipoint covalent attachments on highly activated glyoxyl agarose gels. Initial immobilization resulted only in slight stabilization in relation to the free enzyme, since involvement of all subunits was not achieved. Coating the catalyst with aldehyde-dextran or polyethylenimine, fully stabilized the quaternary structure of the enzyme rendering much more stabilization to the biocatalyst. The catalyst coated with polyethylenimine of molecular weight 1300 is the most stable one exhibiting an interesting half-life of more than 10 days at pH 5.0 and 50 °C, being, therefore, 240-fold more stable than free enzyme. Optimum activity was observed in the pH range 4.0–6.0 and at 55 °C. The catalyst retained its side activity against p-nitrophenyl α-l-arabinofuranoside and it was inhibited by xylose and glucose. Kinetic parameters with p-nitrophenyl β-d-xylopyranoside as substrate were V 0.20 μmol.min mg prot., K 0.45 mM, K 0.82 s, and K/K 1.82 s mM. Xylose release was observed from the hydrolysis of xylooligosaccharides with a decrease in the rate of xylose release by increasing substrate chain-length. Due to the high thermostability and the complete stability after five reuse cycles, the applicability of this biocatalyst in biotechnological processes, such as for the degradation of lignocellulosic biomass, is highly increased.Part of this work was sponsored by the Spanish Ministry of Science and Innovation (Project BIO-2012-36861). C.R.F.T. gratefully acknowledges to CAPES/Ministry of Education, Brazil, through the Program Science Without Borders for the postdoctoral scholarship [Grant 3134-13-0].Peer Reviewe

Continuous production of xylooligosaccharides in a packed bed reactor with immobilized-stabilized biocatalysts of xylanase from Aspergillus versicolor

The production of xylooligosaccharides (XOS) using a packed-bed enzymatic reactor was studied at lab-scale. For this, a xylanase from Aspergillus versicolor was immobilized on different supports. The optimal derivative was xylanase immobilized on glyoxyl-agarose supports. This derivative preserved 85% of its catalytic activity; it was around 700-fold more stable than the soluble enzyme after incubation at 60. °C and was able to be reused for at least 10 1. h-cycles retaining full catalytic activity. About 18% of oligosaccharides with prebiotic interest (X2-X6) were produced by the glyoxyl derivative in batch hydrolysis. The production of xylobiose was 2.5-fold higher using the immobilized preparation than with soluble enzyme and small concentrations of xylose (<0.1%) were observed only at the end of the reaction. The derivative was employed on a packed bed reactor, and the continuous operation with no recirculation reached 56% and 70% of the end of reaction with flow rates of 60. mL/h and 12. mL/h, respectively. In continuous operation with recirculation at a flow rate of 60. mL/h, the reaction was completed after four hours. © 2013 Elsevier B.V

Immobilization and stabilization of a bimolecular aggregate of the lipase from Pseudomonas fluorescens by multipoint covalent attachment

The soluble lipase from Pseudomonas fluorescens (PFL) forms bimolecular aggregates in which the hydrophobic active centers of the enzyme monomers are in close contact. This bimolecular aggregate could be immobilized by multipoint covalent linkages on glyoxyl supports at pH 8.5. The monomer of PFL obtained by incubation of the soluble enzyme in the presence of detergent (0.5% TRITON X-100) could not be immobilized under these conditions. The bimolecular aggregate has two amino terminal residues in the same plane. A further incubation of the immobilized derivative under more alkaline conditions (e.g., pH 10.5) allows a further multipoint attachment of lysine (Lys) residues located in the same plane as the amino terminal residues. Monomeric PFL was immobilized at pH 10.5 in the presence of 0.5% TRITON X-100. The properties of both PFL derivatives were compared. In general, the bimolecular derivatives were more active, more selective and more stable both in water and in organic solvents than the monomolecular ones. The bimolecular derivative showed twice the activity and a much higher selectivity (100 versus 20) for the hydrolysis of R,S-2-hydroxy-4-phenylbutyric acid ethyl ester (HPBEt) in aqueous media at pH 5.0 compared to the monomeric derivative. In experiments measuring thermal inactivation at 75 °C, the bimolecular derivative was 5-fold more stable than the monomeric derivative (and 50-fold more stable than a one-point covalently immobilized PFL derivative), and it had a half-life greater than 4 h. In organic solvents (cyclohexane and tert-amyl alcohol), the bimolecular derivative was much more stable and more active than the monomeric derivative in catalyzing the transesterification of olive oil with benzyl alcohol. © 2012 Elsevier Ltd. All rights reserved.This work was sponsored by the Spanish Ministry of Science and Innovation(project AGL-2009-07526), Consolider INGENIO 2010 CSD2007-00063 FUN-C-FOOD (CICYT) and ALIBIRD S2009/AGR-1469. We gratefully recognize the Spanish Ministry of Science and Innovation for the “Ramón y Cajal” contract for Dr. Fernandez-Lorente. We also thank the Brazilian agencies CAPES and CNPq for the scholarship of Lionete N. Lima.Peer Reviewe

Immobilization and stabilization of a bimolecular aggregate of the lipase from Pseudomonas fluorescens by multipoint covalent attachment

The soluble lipase from Pseudomonas fluorescens (PFL) forms bimolecular aggregates in which the hydrophobic active centers of the enzyme monomers are in close contact. This bimolecular aggregate could be immobilized by multipoint covalent linkages on glyoxyl supports at pH 8.5. The monomer of PFL obtained by incubation of the soluble enzyme in the presence of detergent (0.5% TRITON X-100) could not be immobilized under these conditions. The bimolecular aggregate has two amino terminal residues in the same plane. A further incubation of the immobilized derivative under more alkaline conditions (e.g., pH 10.5) allows a further multipoint attachment of lysine (Lys) residues located in the same plane as the amino terminal residues. Monomeric PFL was immobilized at pH 10.5 in the presence of 0.5% TRITON X-100. The properties of both PFL derivatives were compared. In general, the bimolecular derivatives were more active, more selective and more stable both in water and in organic solvents than the monomolecular ones. The bimolecular derivative showed twice the activity and a much higher selectivity (100 versus 20) for the hydrolysis of R,S-2-hydroxy-4-phenylbutyric acid ethyl ester (HPBEt) in aqueous media at pH 5.0 compared to the monomeric derivative. In experiments measuring thermal inactivation at 75 °C, the bimolecular derivative was 5-fold more stable than the monomeric derivative (and 50-fold more stable than a one-point covalently immobilized PFL derivative), and it had a half-life greater than 4 h. In organic solvents (cyclohexane and tert-amyl alcohol), the bimolecular derivative was much more stable and more active than the monomeric derivative in catalyzing the transesterification of olive oil with benzyl alcohol. © 2012 Elsevier Ltd. All rights reserved