Covalent immobilization of hydroperoxide lyase on chitosan hybrid hydrogels and production of C6 aldehydes by immobilized enzyme

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Cross-linked Enzyme Aggregates of Fibrinolytic Protease BC1 Immobilized on Magnetic Chitosan Nanoparticles (CLEAs-Fib-mChi): Synthesis, Purification, and Characterization

Bacterial fibrinolytic proteases achieved more attention in the prevention and treatment of cardiovascular diseases, so purification, characterization, and activity enhancement are of prime importance. In this study, a fibrinolytic serine metalloprotease was purified from the culture supernatant from Bacillus sp. BC1. It was purified to homogeneity by a two-step procedure with a 24-fold increase in specific activity and a 33.1% yield. It showed 28 kDa molecular weight, while its optimal pH and temperature were obtained 8 and 50-60 °C. The cross-link enzyme aggregates of this fibrinolytic BC1 successfully immobilized on magnetic chitosan nanoparticles. A 52% activity enhancement was obtained by immobilized enzyme at pH 6.0, compared to free protease. K_m values of the free and immobilized proteases were obtained about 0.638 and 0.61 mg/ml, respectively. The free and immobilized enzymes did not show any activity concerning transferrin, γ-globulins, and hemoglobin, as blood plasma proteins. The in vitro blood clot lysis test of the free and immobilized proteases showed a maximum of 42 and 50% clot lysis, which was comparatively higher than that revealed by streptokinase and heparin at the same condition. These results indicated that the free and immobilized proteases have the potential to be effective fibrinolytic agents.

Immobilization of Amano lipase AK from Pseudomonas fluorescens on different types of chitosan-containing supports: use in the kinetic resolution of rac-indanol

Amano lipase AK from P. fluorescens was immobilized on different types of chitosan-containing supports. Chitosan lower molecular weight (2.5%), chitosan lower molecular weight/sodium alginate (2.5%/2.5%) and chitosan lower molecular weight/carrageenan (2.5%/2.5%) allowed the highest values of immobilization yields (IY) of 81, 81 and 83%, respectively. Best activity results were achieved using chitosan average molecular weight (5%) and chitosan lower molecular weight/sodium alginate (2.5%/2.5%) as support, with values of 1.40 and 1.30 U_pNPB/g_gel and with recovery activities of 45.75 and 35.6%, respectively. These derivatives were evaluated in the kinetic resolution of rac-indanol to obtain a key intermediate in the synthesis of a drug used in the treatment of Parkinson's disease. The most efficient derivatives in the kinetic resolution were lipase immobilized on chitosan average molecular weight (5.0%) and chitosan low molecular weight/sodium alginate, the latter leading to obtaining both (S)-indanol and (R)-indanyl acetate with > 99% ee and 50% conversion.

Utilization of different polymers for the improvement of catalytic properties and recycling efficiency of bacterial maltase

Current study deals with the comparative study related to immobilization of maltase using synthetic (polyacrylamide) and non-synthetic (calcium alginate, agar-agar and agarose) polymers via entrapment technique. Polyacrylamide beads were formed by cross-linking of monomers, agar-agar and agarose through solidification while alginate beads were prepared by simple gelation. Results showed that the efficiency of enzyme significantly improved after immobilization and among all tested supports agar-agar was found to be the most promising and biocompatible for maltase in terms of immobilization yield (82.77%). The catalytic behavior of maltase was slightly shifted in terms of reaction time (free enzyme, agarose and polyacrylamide: 5.0 min; agar-agar and alginate: 10.0 min), pH (free enzyme, alginate and polyacrylamide: 6.5; agar-agar, agarose: 7.0) and temperature (free enzyme: 45 °C; alginate: 50 °C; polyacrylamide: 55 °C; agarose: 60 °C; agar-agar: 65 °C). Stability profile of immobilized maltase also revealed that all the supports utilized have significantly enhanced the activity of maltase at higher temperatures then its free counterpart. However, recycling data showed that agar-agar entrapped maltase retained 20.0% of its initial activity even after 10 cycles followed by agarose (10.0%) while polyacrylamide and alginate showed no activity after 8 and 6 cycles respectively.

Improvement of catalytic properties of starch hydrolyzing fungal amyloglucosidase: Utilization of agar-agar as an organic matrix for immobilization

In this study, amyloglucosidase was immobilized within agar-agar through entrapment technique for the hydrolysis of soluble starch. Enzymatic activities of soluble and entrapped amyloglucosidase were compared using soluble starch as a substrate. Partially purified enzyme was immobilized and maximum immobilization yield (80%) was attained at 40 gL^-1 of agar-agar. Enzyme catalysis reaction time shifted from 5.0 min to 10 min after immobilization. Similarly, a five-degree shift in temperature (60 °C-65 °C) and a 0.5 unit increase in pH (pH-5.0 to pH-5.5) were also observed. Substrate saturation kinetics revealed that K_m of entrapped amyloglucosidase increased from 1.41 mg ml^-1 (soluble enzyme) to 3.39 mg ml^-1 (immobilized enzyme) whereas, V_max decreased from 947 kU mg^-1 (soluble enzyme) to 698 kU mg^-1 (immobilized enzyme). Entrapped amyloglucosidase also exhibited significant catalytic performance during thermal and storage stability when compared with soluble enzyme. Reusability of entrapped amyloglucosidase for hydrolysis of soluble starch demonstrated its recycling efficiency up to six cycles which is an exceptional characteristic for continuous bioprocessing of soluble starch into glucose.

Biocatalytic Synthesis of Natural Green Leaf Volatiles Using the Lipoxygenase Metabolic Pathway

In higher plants, the lipoxygenase enzymatic pathway combined actions of several enzymes to convert lipid substrates into signaling and defense molecules called phytooxylipins including short chain volatile aldehydes, alcohols, and esters, known as green leaf volatiles (GLVs). GLVs are synthesized from C18:2 and C18:3 fatty acids that are oxygenated by lipoxygenase (LOX) to form corresponding hydroperoxides, then the action of hydroperoxide lyase (HPL) produces C6 or C9 aldehydes that can undergo isomerization, dehydrogenation, and esterification. GLVs are commonly used as flavors to confer a fresh green odor of vegetable to perfumes, cosmetics, and food products. Given the increasing demand in these natural flavors, biocatalytic processes using the LOX pathway reactions constitute an interesting application. Vegetable oils, chosen for their lipid profile are converted in natural GLVs with high added value. This review describes the enzymatic reactions of GLVs biosynthesis in the plant, as well as the structural and functional properties of the enzymes involved. The various stages of the biocatalytic production processes are approached from the lipid substrate to the corresponding aldehyde or alcoholic aromas, as well as the biotechnological improvements to enhance the production potential of the enzymatic catalysts.

Synthesis and Application of Nanomagnetic Immobilized Phospholipase C

The nanomagnetic carrier (Fe3O4@SiO2@p(GMA)) was prepared by atom transfer radical polymerization, and then, the free phospholipase C (PLC) was immobilized on it proved by the results of FT-IR analysis. The enzyme loading was 135.64 mg/g, the enzyme activity was 8560.7 U/g, the average particle size was 99.86 ± 0.80 nm, and the specific saturation magnetization was 16.00 ± 0.20 emu/g. PLC-Fe3O4@SiO2@p(GMA) showed the highest activities at the pH of 7.5, and tolerance temperature raised to 65°C in soybean lecithin emulsion. Enzymatic degumming with PLC-Fe3O4@SiO2@p(GMA) under the conditions of the enzyme dosage of 110 mg/kg, reaction temperature of 65°C, pH of 7.5, and reaction time of 2.5 h resulted in residual phosphorus of 64.7 mg/kg, 1,2-diacylglycerol (1,2-DAG) contents of 1.07%, and oil yield of 98.1%. Moreover, PLC-Fe3O4@SiO2@p(GMA) still possessed more than 80% of its initial activity after 5 cycles.

Continuous synthesis of hexanal by immobilized hydroperoxide lyase in packed-bed reactor

This study aimed to develop an optimal continuous procedure of immobilized hydroperoxide lyase (HPL)-catalyzed synthesis of hexanal. A central composite design was used to study the combined effect of substrate concentration and the residence time of the reactant on hexanal concentration. The optimum conditions for hexanal synthesis included a 13-HPOD concentration of 43.54 mM and a residence time of 60.99 min. The maximum hexanal concentration was 3560 ± 130 mg/L when 16 U of immobilized HPLwas used. Furthermore, the stability of immobilized HPL was significantly improved in the packed-bed reactor, as evidenced by the slowed enzyme inactivation and prolonged operation time. The immobilized HPL remained activity until 40 mL substrate solution flowed past the packed-bed reactor. The catalyst productivity of hexanal in the packed-bed reactor was 5.35 ± 0.34 mg/U, much higher than that in the batch stirred reactor. This study was greatly meaningful for providing a green method to the large-scale production of hexanal.

New method for the immobilization of pullulanase onto hybrid magnetic (Fe3O4-κ-carrageenan) nanoparticles by electrostatic coupling with pullulanase/chitosan complex

We present a simple method to immobilize pullulanase onto hybrid magnetic (Fe3O4-κ-carrageenan) nanoparticles, involving the in situ synthesis of magnetic carrageenan nanoparticles and the formation of pullulanase/chitosan complex. The complex behavior of pullulanase with chitosan as a function of pH and protein-polysaccharide ratio was studied by turbidimetric titration. Then, the as-prepared immobilized enzymes were characterized by vibrating-sample magnetometer, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometer, and thermogravimetric analysis. It was found that the activity retention of immobilized pullulanase and amount of enzyme loaded reached 95.5% and 96.3 mg/g, respectively, under optimal conditions. The immobilized enzyme exhibited great operational stability (retaining approximately 61% residual activity after ten consecutive reuses), demonstrating that enzyme leakage during the catalysis reaction was efficiently reduced. Furthermore, the activity of immobilized pullulanase was significantly (p < 0.01) higher than that of free pullulanase in a low pH range (pH < 3.0) and temperature over 60 °C, and the immobilized enzymes retained 45% of their initial activity after 5 h at 60 °C, compared to 21% for the free enzyme. These results indicated that immobilized pullulanase was efficient in terms of catalytic activity and can be applied to continuous starch processing applications in the food industry.