Effects of Sulforaphane-Induced Cell Death upon Repeated Passage of Either P-Glycoprotein-Negative or P-Glycoprotein-Positive L1210 Cell Variants.

The expression of the membrane ABCB1 transporter in neoplastic cells is one of the most common causes of reduced sensitivity to chemotherapy. In our previous study, we investigated the effect of a single culture of ABCB1-negative (S) and ABCB1-positive variants of L1210 cells (R and T) in the presence of sulforaphane (SFN). We demonstrated that SFN induces the onset of autophagy more markedly in S cells than in R or T cells. In the current study, we focused on the effect of the repeated culture of S, R and T cells in SFN-containing media. The repeated cultures increased the onset of autophagy compared to the simple culture, mainly in S cells and to a lesser extent in R and T cells, as indicated by changes in the cellular content of 16 and 18 kDa fragments of LC3B protein or changes in the specific staining of cells with monodansylcadaverine. We conclude that SFN affects ABCB1-negative S cells more than ABCB1-positive R and T cells during repeated culturing. Changes in cell sensitivity to SFN appear to be related to the expression of genes for cell-cycle checkpoints, such as cyclins and cyclin-dependent kinases.

Identification of a Novel Two-Peptide Lantibiotic from Vagococcus fluvialis.

Infections caused by multiresistant pathogens have become a major problem in both human and veterinary medicine. Due to the declining efficacy of many antibiotics, new antimicrobials are needed. Promising alternatives or additions to antibiotics are bacteriocins, antimicrobial peptides of bacterial origin with activity against many pathogens, including antibiotic-resistant strains. From a sample of fermented maize, we isolated a Vagococcus fluvialis strain producing a bacteriocin with antimicrobial activity against multiresistant Enterococcus faecium. Whole-genome sequencing revealed the genes for a novel two-peptide lantibiotic. The production of the lantibiotic by the isolate was confirmed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, which revealed distinct peaks at 4,009.4 m/z and 3,181.7 m/z in separate fractions from reversed-phase chromatography. The combination of the two peptides resulted in a 1,200-fold increase in potency, confirming the two-peptide nature of the bacteriocin, named vagococcin T. The bacteriocin was demonstrated to kill sensitive cells by the formation of pores in the cell membrane, and its inhibition spectrum covers most Gram-positive bacteria, including multiresistant pathogens. To our knowledge, this is the first bacteriocin characterized from Vagococcus. IMPORTANCE Enterococci are common commensals in the intestines of humans and animals, but in recent years, they have been identified as one of the major causes of hospital-acquired infections due to their ability to quickly acquire virulence and antibiotic resistance determinants. Many hospital isolates are multiresistant, thereby making current therapeutic options critically limited. Novel antimicrobials or alternative therapeutic approaches are needed to overcome this global problem. Bacteriocins, natural ribosomally synthesized peptides produced by bacteria to eliminate other bacterial species living in a competitive environment, provide such an alternative. In this work, we purified and characterized a novel two-peptide lantibiotic produced by Vagococcus fluvialis LMGT 4216 isolated from fermented maize. The novel lantibiotic showed a broad spectrum of inhibition of Gram-positive strains, including vancomycin-resistant Enterococcus faecium, demonstrating its therapeutic potential.

Yeast GH30 Xylanase from Sugiyamaella lignohabitans Is a Glucuronoxylanase with Auxiliary Xylobiohydrolase Activity.

Xylanases are the enzymes that catalyze the breakdown of the main hemicellulose present in plant cell walls. They have attracted attention due to their biotechnological potential for the preparation of industrially interesting products from lignocellulose. While many xylanases have been characterized from bacteria and filamentous fungi, information on yeast xylanases is scarce and no yeast xylanase belonging to glycoside hydrolase (GH) family 30 has been described so far. Here, we cloned, expressed and characterized GH30 xylanase SlXyn30A from the yeast Sugiyamaella lignohabitans. The enzyme is active on glucuronoxylan (8.4 U/mg) and rhodymenan (linear ß-1,4-1,3-xylan) (3.1 U/mg) while its activity on arabinoxylan is very low (0.03 U/mg). From glucuronoxylan SlXyn30A releases a series of acidic xylooligosaccharides of general formula MeGlcA2Xyln. These products, which are typical for GH30-specific glucuronoxylanases, are subsequently shortened at the non-reducing end, from which xylobiose moieties are liberated. Xylobiohydrolase activity was also observed during the hydrolysis of various xylooligosaccharides. SlXyn30A thus expands the group of glucuronoxylanases/xylobiohydrolases which has been hitherto represented only by several fungal GH30-7 members.

Improved Production of Recombinant Myrosinase in Pichia pastoris.

The effect of the deletion of a 57 bp native signal sequence, which transports the nascent protein through the endoplasmic reticulum membrane in plants, on improved AtTGG1 plant myrosinase production in Pichia pastoris was studied. Myrosinase was extracellularly produced in a 3-liter laboratory fermenter using α-mating factor as the secretion signal. After the deletion of the native signal sequence, both the specific productivity (164.8 U/L/h) and volumetric activity (27 U/mL) increased more than 40-fold compared to the expression of myrosinase containing its native signal sequence in combination with α-mating factor. The deletion of the native signal sequence resulted in slight changes in myrosinase properties: the optimum pH shifted from 6.5 to 7.0 and the maximal activating concentration of ascorbic acid increased from 1 mM to 1.5 mM. Kinetic parameters toward sinigrin were determined: 0.249 mM (Km) and 435.7 U/mg (Vmax). These results could be applied to the expression of other plant enzymes.

Applications of Ionic Liquids in Whole-Cell and Isolated Enzyme Biocatalysis.

Ionic liquids have unique chemical properties that have fascinated scientists in many fields. The effects of adding ionic liquids to biocatalysts are many and varied. The uses of ionic liquids in biocatalysis include improved separations and phase behaviour, reduction in toxicity, and stabilization of protein structures. As the ionic liquid state of the art has progressed, concepts of what can be achieved in biocatalysis using ionic liquids have evolved and more beneficial effects have been discovered. In this review ionic liquids for whole-cell and isolated enzyme biocatalysis will be discussed with an emphasis on the latest developments, and a look to the future.

Production of Aldehydes by Biocatalysis.

The production of aldehydes, highly reactive and toxic chemicals, brings specific challenges to biocatalytic processes. Absence of natural accumulation of aldehydes in microorganisms has led to a combination of in vitro and in vivo strategies for both, bulk and fine production. Advances in genetic and metabolic engineering and implementation of computational techniques led to the production of various enzymes with special requirements. Cofactor synthesis, post-translational modifications and structure engineering are applied to prepare active enzymes for one-step or cascade reactions. This review presents the highlights in biocatalytical production of aldehydes with the potential to shape future industrial applications.

Optimisation of Recombinant Myrosinase Production in Pichia pastoris.

Myrosinase is a plant defence enzyme catalysing the hydrolysis of glucosinolates, a group of plant secondary metabolites, to a range of volatile compounds. One of the products, isothiocyanates, proved to have neuroprotective and chemo-preventive properties, making myrosinase a pharmaceutically interesting enzyme. In this work, extracellular expression of TGG1 myrosinase from Arabidopsis thaliana in the Pichia pastoris KM71H (MutS) strain was upscaled to a 3 L laboratory fermenter for the first time. Fermentation conditions (temperature and pH) were optimised, which resulted in a threefold increase in myrosinase productivity compared to unoptimised fermentation conditions. Dry cell weight increased 1.5-fold, reaching 100.5 g/L without additional glycerol feeding. Overall, a specific productivity of 4.1 U/Lmedium/h was achieved, which was 102.5-fold higher compared to flask cultivations.

Production of Enantiopure Chiral Epoxides with E. coli Expressing Styrene Monooxygenase.

Styrene monooxygenases are a group of highly selective enzymes able to catalyse the epoxidation of alkenes to corresponding chiral epoxides in excellent enantiopurity. Chiral compounds containing oxirane ring or products of their hydrolysis represent key building blocks and precursors in organic synthesis in the pharmaceutical industry, and many of them are produced on an industrial scale. Two-component recombinant styrene monooxygenase (SMO) from Marinobacterium litorale was expressed as a fused protein (StyAL2StyB) in Escherichia coli BL21(DE3). By high cell density fermentation, 35 gDCW/L of biomass with overexpressed SMO was produced. SMO exhibited excellent stability, broad substrate specificity, and enantioselectivity, as it remained active for months and converted a group of alkenes to corresponding chiral epoxides in high enantiomeric excess (˃95-99% ee). Optically pure (S)-4-chlorostyrene oxide, (S)-allylbenzene oxide, (2R,5R)-1,2:5,6-diepoxyhexane, 2-(3-bromopropyl)oxirane, and (S)-4-(oxiran-2-yl)butan-1-ol were prepared by whole-cell SMO.

Semi-Continuous Flow Biocatalysis with Affinity Co-Immobilized Ketoreductase and Glucose Dehydrogenase.

The co-immobilization of ketoreductase (KRED) and glucose dehydrogenase (GDH) on highly cross-linked agarose (sepharose) was studied. Immobilization of these two enzymes was performed via affinity interaction between His-tagged enzymes (six histidine residues on the N-terminus of the protein) and agarose matrix charged with nickel (Ni2+ ions). Immobilized enzymes were applied in a semicontinuous flow reactor to convert the model substrate; α-hydroxy ketone. A series of biotransformation reactions with a substrate conversion of >95% were performed. Immobilization reduced the requirement for cofactor (NADP+) and allowed the use of higher substrate concentration in comparison with free enzymes. The immobilized system was also tested on bulky ketones and a significant enhancement in comparison with free enzymes was achieved.

Dual Substrate Specificity of the Rutinosidase from Aspergillus niger and the Role of Its Substrate Tunnel.

Rutinosidases (α-l-rhamnopyranosyl-(1-6)-ß-d-glucopyranosidases, EC 3.2.1.168, CAZy GH5) are diglycosidases that cleave the glycosidic bond between the disaccharide rutinose and the respective aglycone. Similar to many retaining glycosidases, rutinosidases can also transfer the rutinosyl moiety onto acceptors with a free -OH group (so-called transglycosylation). The recombinant rutinosidase from Aspergillus niger (AnRut) is selectively produced in Pichia pastoris. It can catalyze transglycosylation reactions as an unpurified preparation directly from cultivation. This enzyme exhibits catalytic activity towards two substrates; in addition to rutinosidase activity, it also exhibits ß-d-glucopyranosidase activity. As a result, new compounds are formed by ß-glucosylation or rutinosylation of acceptors such as alcohols or strong inorganic nucleophiles (NaN3). Transglycosylation products with aliphatic aglycones are resistant towards cleavage by rutinosidase, therefore, their side hydrolysis does not occur, allowing higher transglycosylation yields. Fourteen compounds were synthesized by glucosylation or rutinosylation of selected acceptors. The products were isolated and structurally characterized. Interactions between the transglycosylation products and the recombinant AnRut were analyzed by molecular modeling. We revealed the role of a substrate tunnel in the structure of AnRut, which explained the unusual catalytic properties of this glycosidase and its specific transglycosylation potential. AnRut is attractive for biosynthetic applications, especially for the use of inexpensive substrates (rutin and isoquercitrin).

Transglycosidase activity of glycosynthase-type mutants of a fungal GH20 ß-N-acetylhexosaminidase.

ß-N-Acetylhexosaminidases (CAZy GH20, EC 3.2.1.52) are exo-glycosidases specific for cleaving N-acetylglucosamine and N-acetylgalactosamine moieties of various substrates. The ß-N-acetylhexosaminidase from the filamentous fungus Talaromyces flavus (TfHex), a model enzyme in this study, has a broad substrate flexibility and outstanding synthetic ability. We have designed and characterized seven glycosynthase-type variants of TfHex mutated at the catalytic aspartate residue that stabilizes the oxazoline reaction intermediate. Most of the obtained enzyme variants lost the majority of their original hydrolytic activity towards the standard substrate p-nitrophenyl 2-acetamido-2-deoxy-ß-D-glucopyranoside (pNP-ß-GlcNAc); moreover, the mutants were not active with the proposed glycosynthase donor 2-acetamido-2-deoxy-d-glucopyranosyl-α-fluoride (GlcNAc-α-F) either as would be expected in a glycosynthase. Importantly, the mutant enzymes instead retained a strong transglycosylation activity towards the standard substrate pNP-ß-GlcNAc. In summary, five out of seven prepared TfHex variants bearing mutation at the catalytic Asp370 residue acted as efficient transglycosidases, which makes them excellent tools for the synthesis of chitooligosaccharides, with the advantage of processing an inexpensive, stable and commercially available pNP-ß-GlcNAc.

A coupled enzymatic reaction of tyrosinase and glucose dehydrogenase for the production of hydroxytyrosol.

Hydroxytyrosol (HT) is a diphenolic compound prevalent mainly in olives with pronounced antioxidant activity and proven benefits for human health. Current production limitations have motivated studies concerning the hydroxylation of tyrosol to HT with tyrosinase; however, accumulation of the diphenol is restricted due to its rapid subsequent oxidation to 3,4-quinone-phenylethanol. In this study, a continuous two-enzyme reaction system of sol-gel-immobilized tyrosinase and glucose dehydrogenase (GDH) was developed for the synthesis of HT. Purified tyrosinase from Bacillus megaterium (TyrBm) and E. coli cell extract expressing GDH from B. megaterium were encapsulated in a sol-gel matrix based on triethoxysilane precursors. While tyrosinase oxidized tyrosol to 3,4-quinone-phenylethanol, GDH catalyzed the simultaneous reduction of the cofactor NAD+ to NADH, which was the reducing agent enabling the accumulation of HT. Using 50 mM tyrosol, the immobilized system under optimized conditions, enabled a final HT yield of 7.68 g/L with productivity of 2.30 mg HT/mg TyrBm beads. Furthermore, the immobilized bi-enzyme system showed the feasibility for HT production from 1 mM tyrosol using a 0.5-L bioreactor as well as stable activity over 8 repeated cycles. The production of other diphenols with commercial importance such as L-dopa (3,4-dihydroxyphenylalanine) or piceatannol may be synthesized with this efficient approach.

Bioproduction of Quercetin and Rutinose Catalyzed by Rutinosidase: Novel Concept of "Solid State Biocatalysis".

Quercetin is a flavonoid largely employed as a phytochemical remedy and a food or dietary supplement. We present here a novel biocatalytic methodology for the preparation of quercetin from plant-derived rutin, with both substrate and product being in mostly an undissolved state during biotransformation. This "solid-state" enzymatic conversion uses a crude enzyme preparation of recombinant rutinosidase from Aspergillus niger yielding quercetin, which precipitates from virtually insoluble rutin. The process is easily scalable and exhibits an extremely high space-time yield. The procedure has been shown to be robust and was successfully tested with rutin concentrations of up to 300 g/L (ca 0.5 M) at various scales. Using this procedure, pure quercetin is easily obtained by mere filtration of the reaction mixture, followed by washing and drying of the filter cake. Neither co-solvents nor toxic chemicals are used, thus the process can be considered environmentally friendly and the product of "bio-quality." Moreover, rare disaccharide rutinose is obtained from the filtrate at a preparatory scale as a valuable side product. These results demonstrate for the first time the efficiency of the "Solid-State-Catalysis" concept, which is applicable virtually for any biotransformation involving substrates and products of low water solubility.

Cloning and upscale production of monoamine oxidase N (MAO-N D5) by Pichia pastoris.

OBJECTIVE: To clone monoamine oxidase N, that catalyses the selective oxidative deamination or deracemisation of amines into imines, in Pichia pastoris and prove the importance of choosing the proper expression system for its recombinant production. RESULTS: Monoamine oxidase, originating from Aspergillus niger and subjected to directed evolution (MAO-N D5), was cloned and expressed in Pichia pastoris CBS7435 MutS strain for the first time. Various transformants were screened at microscale level. The production of the clone expressing the most active enzyme was scaled-up to a 1.5 l fermenter and preparation of MAO-N D5 as a crude enzyme extract was optimised. The obstacles in the production of the enzyme in both expression systems, Escherichia coli and P. pastoris, are discussed and demonstrated. CONCLUSIONS: There was an improvement in specific productivity, which was 83 times higher in P. pastoris, clearly proving the importance of choosing the right expression host system for the specific enzymes.

Immobilization of cells and enzymes to LentiKats®.

Biocatalyst immobilization is one of the techniques, which can improve whole cells or enzyme applications. This method, based on the fixation of the biocatalyst into or onto various materials, may increase robustness of the biocatalyst, allows its reuse, or improves the product yield. In recent decades, a number of immobilization techniques have been developed. They can be divided according to the used natural or synthetic material and principle of biocatalyst fixation in the particle. One option, based on the entrapment of cells or enzymes into a synthetic polyvinyl alcohol lens with original shape, is LentiKats® immobilization. This review describes the preparation principle of these particles and summarizes existing successful LentiKats® immobilizations. In addition, examples are compared with other immobilization techniques or free biocatalysts, pointing to the advantages and disadvantages of LentiKats®.

The effect of cultivation media and washing whole-cell biocatalysts on monoamine oxidase catalyzed oxidative desymmetrization of 3-azabicyclo[3,3,0]octane.

It is well known that washing whole-cells containing enzyme activities after fermentation, but prior to biocatalysis can improve their activity in the subsequent reaction. In this paper, we quantify the impact of both the fermentation media and cell washing on the performance of whole-cell biocatalysis. The results are illustrated using a recombinant monoamine oxidase (expressed in Escherichia coli, used in resting state) for the oxidative desymmetrization of 3-azabicyclo[3,3,0]octane. It was shown that the need for washing biocatalyst prior to use in a reaction is dependent upon growth medium. Unlike cells grown in LB medium, washing of the cells was essential for cells grown on TB medium. With TB media, washing the cells improved the final conversion by approximately a factor of two. Additionally, over 50-fold improvement was achieved in initial activity. A potential reason for this improvement in activity was identified to be the increase in transfer of substrates across the cell membrane as a result of cell washing.

Upscale of recombinant α-L-rhamnosidase production by Pichia pastoris Mut(S) strain.

Pichia pastoris is currently one of the most preferred microorganisms for recombinant enzyme production due to its efficient expression system. The advantages include the production of high amounts of recombinant proteins containing the appropriate posttranslational modifications and easy cultivation conditions. α-L-Rhamnosidase is a biotechnologically important enzyme in food and pharmaceutical industry, used for example in debittering of citrus fruit juices, rhamnose pruning from naringin, or enhancement of wine aromas, creating a demand for the production of an active and stable enzyme. The production of recombinant α-L-rhamnosidase cloned in the Mut(S) strain of P. pastoris KM71H was optimized. The encoding gene is located under the control of the AOX promoter, which is induced by methanol whose concentration is instrumental for these strain types. Fermentation was upscaled in bioreactors employing various media and several methanol-feeding strategies. It was found that fed batch with BSM media was more effective compared to BMMH (Buffered Methanol-complex Medium) media due to lower cost and improved biomass formation. In BSM (Basal Salt Medium) medium, the dry cell weight reached approximately 60 g/L, while in BMMH it was only 8.3 g/L, without additional glycerol, which positively influenced the amount of enzyme produced. New methanol feeding strategy, based on the level of dissolved oxygen was developed in this study. This protocol that is entirely independent on methanol monitoring was up scaled to a 19.5-L fermenter with 10-L working volume with the productivity of 13.34 mgprot/L/h and specific activity of α-L-rhamnosidase of 82 U/mg. The simplified fermentation protocol was developed for easy and effective fermentation of P. pastoris Mut(S) based on dissolved oxygen monitoring in the induction phase of an enzyme production.

Immobilised whole-cell recombinant monoamine oxidase biocatalysis.

This work demonstrates the first example of the immobilisation of MAO-N whole cells to produce a biocatalyst that remained suitable for repetitive use after 11 months of storage and stable up to 15 months after immobilisation. The production of Escherichia coli expressing recombinant MAO-N was scaled up to bioreactors under regulated, previously optimised conditions (10% DO, pH 7), and the amount of biomass was almost doubled compared to flask cultivation. Subsequently, pilot immobilisation of the whole-cell biocatalyst using LentiKats technology was performed. The amount of the immobilised biomass was optimised and the process was scaled up to a production level by immobilising 15 g of dry cell weight per litre of polyvinyl alcohol to produce 3 kg of whole-cell ready-to-use biocatalyst. The immobilised biocatalyst retained its initial activity over six consecutive biotransformations of the secondary amine model compound 3-azabicylo [3,3,0]octane, a building block of the hepatitis C drug telaprevir. Consecutive cultivation cycles in growth conditions not only increased the initial specific activity of biocatalyst produced on the industrial plant by more than 30%, but also significantly increased the rate of the biotransformation compared to the non-propagated biocatalyst.

Butanol production by immobilised Clostridium acetobutylicum in repeated batch, fed-batch, and continuous modes of fermentation.

Clostridium acetobutylicum immobilised in polyvinylalcohol, lens-shaped hydrogel capsules (LentiKats(®)) was studied for production of butanol and other products of acetone-butanol-ethanol fermentation. After optimising the immobilisation protocol for anaerobic bacteria, continuous, repeated batch, and fed-batch fermentations in repeated batch mode were performed. Using glucose as a substrate, butanol productivity of 0.41 g/L/h and solvent productivity of 0.63 g/L/h were observed at a dilution rate of 0.05 h(-1) during continuous fermentation with a concentrated substrate (60 g/L). Through the process of repeated batch fermentation, the duration of fermentation was reduced from 27.8h (free-cell fermentation) to 3.3h (immobilised cells) with a solvent productivity of 0.77 g/L/h (butanol 0.57 g/L/h). The highest butanol and solvent productivities of 1.21 and 1.91 g/L/h were observed during fed-batch fermentation operated in repeated batch mode with yields of butanol (0.15 g/g) and solvents (0.24 g/g), respectively, produced per gram of glucose.

Physical and bioengineering properties of polyvinyl alcohol lens-shaped particles versus spherical polyelectrolyte complex microcapsules as immobilisation matrices for a whole-cell Baeyer-Villiger monooxygenase.

Direct comparison of key physical and chemical-engineering properties of two representative matrices for multipurpose immobilisations was performed for the first time. Polyvinyl alcohol lens-shaped particles LentiKats® and polyelectrolyte complex microcapsules were characterised by advanced techniques with respect to the size distribution of the particles, their inner morphology as revealed by fluorescent probe staining, mechanical resistance, size-exclusion properties, determination of effective diffusion coefficient and environmental scanning electron microscope imaging. While spherical polyelectrolyte complex microcapsules composed of a rigid semipermeable membrane and a liquid core are almost uniform in shape and size (diameter of 0.82 mm; RSD = 5.6 %), lens-shaped LentiKats® are characterised by wider size distribution (diameter of 3.65 mm; RSD = 10.3 % and height of 0.341 mm; RSD = 32.3 %) and showed the same porous structure throughout their whole volume at the mesoscopic (micrometre) level. Despite differences in their inner structure and surface properties, the pore diameter of ∼ 2.75 nm for regular polyelectrolyte complex microcapsules and ∼ 1.89 nm for LentiKats® were similar. These results were used for mathematical modelling, which provided the estimates of the effective diffusion coefficient of sucrose. This value was 1.67 × 10(-10) m(2) s(-1) for polyelectrolyte complex microcapsules and 0.36 × 10(-10) m(2) s(-1) for LentiKats®. Recombinant cells Escherichia coli-overexpressing enzyme cyclopentanone monooxygenase were immobilised in polyelectrolyte complex microcapsules and LentiKats® for comparison of their operational stability using model Baeyer-Villiger oxidation of (±)-cis-bicyclo [3.2.0] hept-2-en-6-one to regioisomeric lactones as important chiral synthons for potential pharmaceuticals. Both immobilisation matrices rendered high operational stability for whole-cell biocatalyst with no reduction in the biooxidation rate over 18 repeated reaction cycles.