Development of a Novel Bi-Enzymatic Nanobiocatalyst for the Efficient Bioconversion of Oleuropein to Hydroxytyrosol

Phenol Degradation by Pseudarthrobacter phenanthrenivorans Sphe3

Phenol poses a threat as one of the most important industrial environmental pollutants that must be removed before disposal. Biodegradation is a cost-effective and environmentally friendly approach for phenol removal. This work aimed at studying phenol degradation by Pseudarthrobacter phenanthrenivorans Sphe3 cells and also, investigating the pathway used by the bacterium for phenol catabolism. Moreover, alginate-immobilized Sphe3 cells were studied in terms of phenol degradation efficiency compared to free cells. Sphe3 was found to be capable of growing in the presence of phenol as the sole source of carbon and energy, at concentrations up to 1500 mg/L. According to qPCR findings, both pathways of ortho- and meta-cleavage of catechol are active, however, enzymatic assays and intermediate products identification support the predominance of the ortho-metabolic pathway for phenol degradation. Alginate-entrapped Sphe3 cells completely degraded 1000 mg/L phenol after 192 h, even though phenol catabolism proceeds slower in the first 24 h compared to free cells. Immobilized Sphe3 cells retain phenol-degrading capacity even after 30 days of storage and also can be reused for at least five cycles retaining more than 75% of the original phenol-catabolizing capacity.

Immobilization of Candida antarctica Lipase A onto Macroporous Resin NKA-9: Esterification and Glycerolysis Performance Study

In this study, lipase A from Candida antarctica (CALA) was immobilized onto the macroporous resin NKA-9. Immobilization conditions (pH, time and CALA concentration) were studied, enzymatic activity and immobilization efficiency (IE) up to 968.89 U/g and 53.19% were respectively obtained under optimal conditions (immobilization pH 5.0, time 5 h and CALA concentration at 30 mg/mL). Then, the NKA-9 supported CALA (CALA@NKA-9) samples were used to catalyze glycerolysis in solvent-free system. With 0.25 g of the present CALA@NKA-9 (soybean oil 3.52 g and glycerol 0.184 g) and after 12 h reaction at 50 °C, diacylglycerols (DAG) content up to 64.37% and triacylglycerols (TAG) conversion at 83.33% were obtained. The relationship between temperature and TAG conversion was LnV ₀ = 13.9310-6.4212/T for CALA@NKA-9. Meanwhile, the activation energy (Ea) of CALA@NKA-9 was calculated to be 53.39 kJ/mol. In addition, reusability in the glycerolysis reaction was also evaluated, and 57.82% of the initial glycerolysis activity was retained after 9 consecutive applications. Furthermore, the CALA@NKA-9 was also used to catalyze the esterification (esterification of fatty acids with glycerol), however, the present CALA@NKA-9 cannot initiate the esterification. Therefore, the present CALA@NKA-9 is shown to be potential for DAG production through glycerolysis reaction.

A flexible kinetic assay efficiently sorts prospective biocatalysts for PET plastic subunit hydrolysis

Esterase enzymes catalyze diverse hydrolysis reactions with important biological, commercial, and biotechnological applications. For the improvement of these biocatalysts, there is a need for widely accessible, inexpensive, and adaptable activity screening assays that identify enzymes with particular substrate specificities. Natural systems for biopolymer bioconversion, and likely those designed to mimic them, depend on cocktails of enzymes, each of which specifically targets the intact material as well as water-soluble subunits of varying size. In this work, we have adapted a UV/visible assay using pH-sensitive sulfonphthalein dyes for the real-time quantification of ester hydrolysis of bis-(2-hydroxyethyl) terephthalate (BHET), a subunit of polyethylene terephthalate (PET) plastic. We applied this method to a diverse set of known PET hydrolases and commercial esterases in a microplate format. The approach identified four PET hydrolases and one commercial esterase with high levels of specificity for BHET hydrolysis. Five additional PET hydrolases and three commercial esterases, including a thermophilic enzyme, effectively hydrolyzed both BHET and its monoester product MHET (mono-(2-hydroxyethyl) terephthalate). Specific activities were discernible within one hour and reactions reached an unequivocal endpoint well within 24 hours. The results from the UV/visible method correlated well with conventional HPLC analysis of the reaction products. We examined the suitability of the method toward variable pH, temperature, enzyme preparation method, mono- and multi-ester substrate type, and level of sensitivity versus stringency, finding the assay to be easily adaptable to diverse screening conditions and kinetic measurements. This method offers an accurate, easily accessible, and cost-effective route towards high-throughput library screening to support the discovery, directed evolution, and protein engineering of these critical biocatalysts.

Characterization of Gentisate 1,2-Dioxygenase from Pseudarthrobacter phenanthrenivorans Sphe3 and Its Stabilization by Immobilization on Nickel-Functionalized Magnetic Nanoparticles

The aim of this study was the biochemical and kinetic characterization of the gentisate 1,2-dioxygenase (GDO) from Pseudarthrobacter phenanthrenivorans Sphe3 and the development of a nanobiocatalyst by its immobilization on Ni2+-functionalized Fe3O4-polydopamine magnetic nanoparticles (Ni2+-PDA-MNPs). This is the first GDO to be immobilized. The gene encoding the GDO was cloned with an N-terminal His-tag and overexpressed in E. coli. The nanoparticles showed a high purification efficiency of GDO from crude cell lysates with a maximum activity recovery of 97%. The immobilized enzyme was characterized by Fourier transform infrared spectroscopy (FTIR). The reaction product was identified by 1H NMR. Both free and immobilized GDO exhibited Michaelis–Menten kinetics with Km values of 25.9 ± 4.4 and 82.5 ± 14.2 μM and Vmax values of 1.2 ± 0.1 and 0.03 ± 0.002 mM*s−1, respectively. The thermal stability of the immobilized GDO was enhanced at 30 °C, 40 °C, and 50 °C, compared to the free GDO. Stored at −20 °C, immobilized GDO retained more than 60% of its initial activity after 30 d, while the free enzyme completely lost its activity after 10 d. Furthermore, the immobilized nanoparticle–enzyme conjugate retained more than 50% enzyme activity up to the fifth cycle.

A Bi-enzymatic Immobilized Nanobiocatalyst for the Biotransformation of Oleuropein to Hydroxytyrosol

Multi-enzymatic assemblies offer the opportunity of bringing in proximity several enzymes that are enabled to work together for the catalysis of multi-step reactions. Especially, the development of robust nanobiocatalytic systems comprising of several enzymes has gained considerable attention over the last few years for the catalysis of complex reactions and the production of high added-value products. In the present chapter, we describe the methodology for the development of a bi-enzymatic nanobiocatalyst consisting of the enzymes β-glucosidase from Thermotoga maritima and lipase A from Candida antarctica (CalA) co-immobilized on chitosan-coated magnetic nanoparticles. This nanobiocatalyst can be efficiently applied for the biotransformation of oleuropein to hydroxytyrosol, a reaction of increased biotechnological interest. Several techniques, as well as methodologies that are required for the characterization of the structure and the activity of such systems are also comprehensively described.