Enzyme encapsulation in permeabilized Saccharomyces cerevisiae cells

Effects of trehalose and ergosterol on pinene stress of Candida glycerinogenes

Pinene is a commercially important monoterpene that can be prepared using engineered bacterial and yeast species; however, high pinene levels can adversely affect the stability and permeability of microbial membranes leading to significantly reduced growth yields. This study reports that the fluidities and permeabilities of cell membranes of Candida glycerinogenes decrease as pinene levels increase resulting in adverse effects on cell growth. Exposure of cells to pinene results in upregulation of the genes encoding ergosterol and trehalose whose production helps stabilize their cell membranes. Exogenous addition of ergosterol and trehalose to pinene-treated cells also reduces the fluidity and permeability of the cell membrane, whilst also reducing production of intracellular reactive oxygen species. This led to the finding that the biomass of yeast cells cultivated in shake flask systems are improved by exogenous addition of trehalose and ergosterol. Overexpression of genes that encode trehalose and ergosterol produced a recombinant C. glycerinogenes strain that was found to tolerate higher concentrations of  pinene.

Yeast Cells in Microencapsulation. General Features and Controlling Factors of the Encapsulation Process

Besides their best-known uses in the food and fermentation industry, yeasts have also found application as microcapsules. In the encapsulation process, exogenous and most typically hydrophobic compounds diffuse and end up being passively entrapped in the cell body, and can be released upon application of appropriate stimuli. Yeast cells can be employed either living or dead, intact, permeabilized, or even emptied of all their original cytoplasmic contents. The main selling points of this set of encapsulation technologies, which to date has predominantly targeted food and-to a lesser extent-pharmaceutical applications, are the low cost, biodegradability and biocompatibility of the capsules, coupled to their sustainable origin (e.g., spent yeast from brewing). This review aims to provide a broad overview of the different kinds of yeast-based microcapsules and of the main physico-chemical characteristics that control the encapsulation process and its efficiency.

Yeast cells for encapsulation of bioactive compounds in food products: A review

Nowadays bioactive compounds have gained great attention in food and drug industries owing to their health aspects as well as antimicrobial and antioxidant attributes. Nevertheless, their bioavailability, bioactivity, and stability can be affected in different conditions and during storage. In addition, some bioactive compounds have undesirable flavor that restrict their application especially at high dosage in food products. Therefore, food industry needs to find novel techniques to overcome these problems. Microencapsulation is a technique, which can fulfill the mentioned requirements. Also, there are many wall materials for use in encapsulation procedure such as proteins, carbohydrates, lipids, and various kinds of polymers. The utilization of food-grade and safe carriers have attracted great interest for encapsulation of food ingredients. Yeast cells are known as a novel carrier for microencapsulation of bioactive compounds with benefits such as controlled release, protection of core substances without a significant effect on sensory properties of food products. Saccharomyces cerevisiae was abundantly used as a suitable carrier for food ingredients. Whole cells as well as cell particles like cell wall and plasma membrane can act as a wall material in encapsulation process. Compared to other wall materials, yeast cells are biodegradable, have better protection for bioactive compounds and the process of microencapsulation by them is relatively simple. The encapsulation efficiency can be improved by applying some pretreatments of yeast cells. In this article, the potential application of yeast cells as an encapsulating material for encapsulation of bioactive compounds is reviewed.

Minimalist Protocell Design: A Molecular System Based Solely on Proteins that Form Dynamic Vesicular Membranes Embedding Enzymatic Functions

Life in its molecular context is characterized by the challenge of orchestrating structure, energy and information processes through compartmentalization and chemical transformations amenable to mimicry of protocell models. Here we present an alternative protocell model incorporating dynamic membranes based on amphiphilic elastin-like proteins (ELPs) rather than phospholipids. For the first time we demonstrate the feasibility of combining vesicular membrane formation and biocatalytic activity with molecular entities of a single class: proteins. The presented self-assembled protein-membrane-based compartments (PMBCs) accommodate either an anabolic reaction, based on free DNA ligase as an example of information transformation processes, or a catabolic process. We present a catabolic process based on a single molecular entity combining an amphiphilic protein with tobacco etch virus (TEV) protease as part of the enclosure of a reaction space and facilitating selective catalytic transformations. Combining compartmentalization and biocatalytic activity by utilizing an amphiphilic molecular building block with and without enzyme functionalization enables new strategies in bottom-up synthetic biology, regenerative medicine, pharmaceutical science and biotechnology.

In vitro anti-Leishmania activity of T6 synthetic compound encapsulated in yeast-derived β-(1,3)-d-glucan particles

The objective of this study was to encapsulate a synthetic compound, the 4-[(2E)-N'-(2,2'-bithienyl-5-methylene)hydra-zinecarbonyl]-6,7-dihydro-1-phenyl-1H-pyrazolo[3,4-d]pyridazin-7-one (T6) in glucan-rich particles mainly composed by the cell wall of Saccharomyces cerevisiae (GPs) and to study their individual and combined activity on Leishmania infantum. The possible mechanism of action of T6 was also investigated. Our results showed the activity of T6 compound in both promastigote (IC₅₀ = 2.5 μg/mL) and intracellular amastigote (IC₅₀ = 1.23 μg/mL) forms. We also found activity against intracellular amastigote forms (IC₅₀ = 8.20 μg/mL) when the T6 compound was encapsulated in GPs. Another interesting finding was the fact that T6 encapsulated in GPs showed a significant decrease in J774A1 macrophage toxicity (CC₅₀ ≥ 18.53 μg/mL) compared to the T6 compound alone (IC₅₀ = 2.27 μg/mL). Through electron microscopy and biochemical methodologies, we verified that the activity of T6 in promastigote forms of L. infantum was characterized by events of cell death by apoptosis like increased ROS production, cell shrinkage, phosphatidylserine exposure and DNA fragmentation. We conclude that T6 can be considered a promising anti-Leishmania compound, and that the use of GPs for drug encapsulation is an interesting approach to the development of new effective and less toxic formulations.

Characterization and oxidative stability of purslane seed oil microencapsulated in yeast cells biocapsules

BACKGROUND

Purslane seed oil, as a potential nutritious source of omega-3 fatty acid, is susceptible to oxidation. Encapsulation in yeast cells is a possible approach for overcoming this problem. In the present study, purslane seed oil was encapsulated in non-plasmolysed, plasmolysed and plasmolysed carboxy methyl cellulose (CMC)-coated Saccharomyces cerevisiae cells and measurements of oil loading capacity (LC), encapsulation efficiency (EE), oxidative stability and the fatty acid composition of oil-loaded microcapsules were made. Furthermore, investigations of morphology and thermal behavior, as well as a Fourier transform-infrared (FTIR) analyses of microcapsules, were performed.

RESULTS

The values of EE, LC were approximately 53-65% and 187-231 g kg^-1_, respectively. Studies found that the plasmolysis treatment increased EE and LC and decreased the mean peroxide value (PV) of microencapsulated oil. The presence of purslane seed oil in yeast microcapsules was confirmed by FTIR spectroscopy and differential scanning calorimetry analyses. The lowest rate of oxidation belonged to the oil-loaded plasmolysed CMC-coated microcapsules (16.73 meqvO₂ kg^-1 ), whereas the highest amount of oxidation regardless of native oil referred to the oil-loaded in non-plasmolysed cells (28.15 meqvO₂ kg^-1 ).

CONCLUSION

The encapsulation of purslane seed oil in the yeast cells of S. cerevisiae can be considered as an efficient approach for extending the oxidative stability of this nutritious oil and facilitating its application in food products. © 2017 Society of Chemical Industry.

Stability and release behavior of encapsulated flavor from spray-dried Saccharomyces cerevisiae and maltodextrin powder

Yeast cells (Saccharomyces cerevisiae), from which β-glucans have been partially extracted, were used to encapsulate flavor inside the lipid bilayer membrane as natural encapsulant. The focus of this study was to investigate the release and stability of flavors (d-limonene and ethyl hexanoate) encapsulated in yeast cells and maltodextrin (MD) (DE = 19) by spray drying. The release behavior of encapsulated flavors from yeast cells was measured at 40, 60, 80, and 105 °C with different moisture content (0, 50, 100, and 200% of powder). Water affected flavor release from the yeast cells. The release rate constants were correlated using Gaussian distribution of the activation energy of the release rate constants. The release of d-limonene from the spray-dried MD powder showed a different trend than that of yeast cells at various temperatures. The activation energies of the release rate constant for ethyl hexanoate and d-limonene from yeast were 55 and 49 kJ/mol, respectively, under a wet condition. The formation rates of limonene oxide and carvone were slower in yeast than that of MD powder at 30 °C after 2 months.

Novel one-pot ATP regeneration system based on three-enzyme cascade for industrial CTP production

OBJECTIVES

To develop a new one-pot polyphosphate kinase (PPK) system with low cost and high efficiency for ATP regeneration in industrial CTP production.

RESULTS

We developed a new one-pot PPK system by applying a three-enzyme cascade (CMK, NDK and PPK) with an in vitro polyP-based ATP regeneration system. The PPK was selected from twenty sources, and was made solvable by fusion expressing with soluble protein and constructing polycistronic plasmids, or co-expressing with molecular chaperones GroES/EL. Activities of other enzymes were optimized by employing fusion expression, tac-pBAD system, Rosetta host and codon optimization. After 24 h, the concentration of CDP and CTP reached 3.8 ± 0.2 and 6.9 ± 0.3 mM l^-1 respectively with a yield of approximately 79%. The molar conversion rate of CTP was 51%, and its yield and conversion rate increased 100% from the traditional system.

CONCLUSIONS

A new one-pot ATP regeneration system applying polyphosphate kinase for CTP production was developed.

Microenvironmental pH changes in immobilized cephalosporin C acylase during a proton-producing reaction and regulation by a two-stage catalytic process

Cephalosporin C acylase (CCA), a proton-producing enzyme, was covalently bound on an epoxy-activated porous support. The microenvironmental pH change in immobilized CCA during the reaction was detected using pH-sensitive fluorescein labeling. The high catalytic velocity of the initial stage of conversion resulted in a sharp intraparticle pH gradient, which was likely the key factor relating to low operational stability. Accordingly, a novel strategy for a two-stage catalytic process was developed to reduce the reaction rate of stage I at a low temperature to preserve enzymatic activity and to shorten the duration of catalysis at a high reaction temperature in stage II. The reaction using the two-stage catalytic process (10-37°C shift at 30min) showed significantly improved stability compared with that of the single-temperature reaction at 37°C (29 batches versus five batches, respectively) and a shorter catalytic period than the reaction at 10°C (40min versus 70min, respectively).

Optimization of permeabilization process of yeast cells for catalase activity using response surface methodology

Biotransformation processes accompanied by whole yeast cells as biocatalyst are a promising area of food industry. Among the chemical sanitizers currently used in food technology, hydrogen peroxide is a very effective microbicidal and bleaching agent. In this paper, permeabilization has been applied to Saccharomyces cerevisiae yeast cells aiming at increased intracellular catalase activity for decomposed H₂O₂. Ethanol, which is non-toxic, biodegradable and easily available, has been used as permeabilization factor. Response surface methodology (RSM) has been applied in determining the influence of different parameters on permeabilization process. The aim of the study was to find such values of the process parameters that would yield maximum activity of catalase during decomposition of hydrogen peroxide. The optimum operating conditions for permeabilization process obtained by RSM were as follows: 53% (v/v) of ethanol concentration, temperature of 14.8 °C and treatment time of 40 min. After permeabilization, the activity of catalase increased ca. 40 times and its maximum value equalled to 4711 U/g.

New aspects of Saccharomyces cerevisiae as a novel carrier for berberine

Background

Berberine was encapsulated in yeast cells of Saccharomyces cerevisiae as novel carriers to be used in different food and drug industries. The microcapsules were characterized by differential scanning calorimetry (DSC), fourier transform infra red spectroscopy (FT-IR) and fluorescence microscopy. The encapsulation factors such as plasmolysis of yeast cells which affects the % encapsulation yield were studied.

Results

Fluorescence microscopy showed the yeast cells became fluorescent after encapsulation process. DSC diagram was representing of new peak for microcapsule which was not the same as berberine and the empty yeast cells peaks, separately. FTIR spectrums of microcapsules and yeast cells were almost the same. The plasmolysed and non plasmolysed microcapsules were loaded with berberine up to about 40.2 ± 0.2% w/w.

Conclusion

Analytical methods proved that berberine was encapsulated in the yeast cells. Fluorescence microscopy and FTIR results showed the entrance of berberine inside the yeasts. DSC diagram indicated the appearance of new peak which is due to the synthesis of new product. Although plasmolysis caused changes in yeast cell structure and properties, it did not enhance berberine loading in the cells. The results confirmed that Saccharomyces cerevisiae could be an efficient and safe carrier for active materials.

New biotransformation process for production of the fragrant compound γ-dodecalactone from 10-hydroxystearate by permeabilized Waltomyces lipofer cells

A new biotransformation process for the production of the flavor lactone was developed by using permeabilized Waltomyces lipofer, which was selected as an efficient γ-dodecalactone-producing yeast among 10 oleaginous yeast strains. The optimal reaction conditions for γ-dodecalactone production by permeabilized W. lipofer cells were pH 6.5, 35°C, 200 rpm, 0.7 M Tris, 60 g/liter of 10-hydroxystearic acid, and 30 g/liter of cells. Under these conditions, nonpermeabilized cells produced 12 g/liter of γ-dodecalactone after 30 h, with a conversion yield of 21% (wt/wt) and a productivity of 0.4 g/liter/h, whereas permeabilized cells obtained after sequential treatments with 50% ethanol and 0.5% Triton X-100 produced 46 g/liter of γ-dodecalactone after 30 h, with a conversion yield of 76% (wt/wt) and a productivity of 1.5 g/liter/h. These values were 3.7- and 3.8-fold higher than those obtained using nonpermeabilized cells. These are the highest reported concentration, conversion yield, and productivity for the production of the bioflavor lactone.

Enzymatic glutathione production using metabolically engineered Saccharomyces cerevisiae as a whole-cell biocatalyst

We developed a novel enzymatic glutathione (GSH) production system using Saccharomyces cerevisiae as a whole-cell biocatalyst, and improved its GSH productivity by metabolic engineering. We demonstrated that the metabolic engineering of GSH pathway and ATP regeneration can significantly improve GSH productivity by up to 1.7-fold higher compared with the parental strain, respectively. Furthermore, the combination of both improvements in GSH pathway and ATP regeneration is more effective (2.6-fold) than either improvement individually for GSH enzymatic production using yeast. The improved whole-cell biocatalyst indicates its great potential for applications to other kinds of ATP-dependent bioproduction.

env1 Mutant of VPS35 gene exhibits unique protein localization and processing phenotype at Golgi and lysosomal vacuole in Saccharomyces cerevisiae

The yeast vacuole is functionally and structurally equivalent to the mammalian lysosome. Delivery of resident and cargo proteins to the lysosome is vital for proper cellular operations, and failure to correctly target proteins to the organelle is correlated with the development of neurodegenerative and lysosomal storage diseases. We previously reported a novel mutant screen for vacuolar trafficking defects in yeast Saccharomyces cerevisiae that resulted in the isolation of env1, an allelic mutant of VPS35. As a member of the retromer complex, Vps35p binds directly to cargos and facilitates their retrograde transport to trans Golgi from endosomes. Our previous studies established that env1 exhibits unique pleiotropic phenotype in comparison to other tested VPS35 alleles including severe growth sensitivity to hygromycin B and internal accumulation of the precursor form of the vacuolar enzyme carboxypeptidase Y. Here, through a combination of sub-cellular fractionation and indirect immunofluorescence microscopy, we confirm and extend the unique phenotype of env1 to processing and localization of additional proteins within the vacuolar trafficking pathway. In comparative studies with a null and an allelic mutant of VPS35, env1 exhibited unique processing defects of retromer-independent vacuolar membrane enzyme alkaline phosphatase at the vacuole and significant Golgi localization of retromer cargos Vps10p and Kex2p despite compromised trafficking at the Golgi and late endosome interface.

Electrochemical characterization of enzymatic activity of yeast cells entrapped in a poly(dimethylsiloxane) microwell on the basis of limited diffusion system

A highly sensitive and quantitative analysis was performed using a poly(dimethylsiloxane) (PDMS) microwell array in a scanning electrochemical microscopy setup. A microelectrode with a relatively large seal radius was used to cover the top of the cylindrical PDMS microwell (96 pL). The voltammogram for 4 mM ferrocyanide resulted in a charge value of 38 nC, suggesting that almost 100% of the reductant in the microwell was converted to the oxidation current. When genetically modified yeast cells were entrapped in the microwell, the accumulation of p-aminophenol (PAP) produced by expressing beta-galactosidase (betaGAL) was successfully observed.

Permeabilization of baker's yeast with N-lauroyl sarcosine

N-Lauroyl sarcosine (LS), a cationic, non-toxic and biodegradable detergent readily permeabilized whole cells of baker's yeast (Saccharomyces cerevisiae). Permeabilization was carried out to increase assayable cellular catalase activity, an enzyme of great physiological and industrial importance, and to release 5'-nucleotides which find food/nutritional applications. The event of permeabilization was concentration, time and temperature dependent. Maximum permeabilization of yeast cells were observed when 1 g wet weight (0.2 g dry wt) of cells were permeabilized with 1.0 ml of 2% LS at 45 degrees C for 15 min. LS-permeabilized cells showed 350-fold increase in catalase activity and the supernatant obtained after permeabilization was rich in 5'-nucleotides. LS-permeabilized baker's yeast cells can be used as a source of biocatalyst and to isolate valuable by-products.

A novel immunodetection screen for vacuolar defects identifies a unique allele of VPS35 in S. cerevisiae

The late endosome and vacuole of yeast Saccharomyces cerevisiae are functionally equivalent to the mammalian late endosome and lysosome. The late endosome is the convergence point of the biosynthetic and endocytic trafficking to the vacuole. Here, we describe a novel immunodetection screen to isolate mutants defective in trafficking the soluble hydrolase carboxypeptidase Y (CPY) at the late endosome to vacuole interface (env mutants). Mutants exhibit vacuolar morphology and endocytosis defects as assayed by electron, fluorescent, and nomarski microscopy. In biochemical assays, they internally accumulate p2CPY in a dense membrane compartment lacking vacuolar properties yet display normal secretion phenotypes. The results suggest vacuolar morphology and function defects that are exclusively at the late endosome/vacuole interface. env mutants define five complementation groups. The first gene of the collection to be cloned, ENV1 is allelic to VPS35 whose established function is in retrograde trafficking from late endosome to trans-Golgi network (TGN). Microscopic, biochemical, and growth analyses establish that env1 is distinct from other alleles of VPS35 in vacuolar morphology, growth characteristics, and internal accumulation of p2CPY. Our results indicate that ENV genes may define new gene functions at the late endosome to vacuole interface.

Permeability issues in whole-cell bioprocesses and cellular membrane engineering

Nutrient uptake and waste excretion are among the many important functions of the cellular membrane. While permitting nutrients into the cell, the cellular membrane system evolves to guide against noxious agents present in the environment from entering the intracellular milieu. The semipermeable nature of the membrane is at odds with biomolecular engineers in their endeavor of using microbes as cell factory. The cellular membrane often retards the entry of substrate into the cellular systems and prevents the product from being released from the cellular system for an easy recovery. Consequently, productivities of whole-cell bioprocesses such as biocatalysis, fermentation, and bioremediations are severely compromised. For example, the rate of whole-cell biocatalysis is usually 1-2 orders of magnitude slower than that of the isolated enzymes. When product export cannot keep pace with the production rate, intracellular product accumulation quickly leads to a halt of production due to product inhibition. While permeabilization via chemical or physical treatment of cell membrane is effective in small-scale process, large-scale implementation is problematic. Molecular engineering approach recently emerged as a much better alternative. Armed with increasingly sophisticated tools, biomolecular engineers are following nature's ingenuity to derive satisfactory solutions to the permeability problem. This review highlights these exciting molecular engineering achievements.

Effect of Agave tequilana juice on cell wall polysaccharides of three Saccharomyces cerevisiae strains from different origins

In this study, a characterization of cell wall polysaccharide composition of three yeasts involved in the production of agave distilled beverages was performed. The three yeast strains were isolated from different media (tequila, mezcal and bakery) and were evaluated for the beta(1,3)-glucanase lytic activity and the beta-glucan/ mannan ratio during the fermentation of Agave tequilana juice and in YPD media (control). Fermentations were performed in shake flasks with 30 g l(-1) sugar concentration of A. tequilana juice and with the control YPD using 30 g l(-1) of glucose. The three yeasts strains showed different levels of beta-glucan and mannan when they were grown in A. tequilana juice in comparison to the YPD media. The maximum rate of cell wall lyses was 50% lower in fermentations with A. tequilana juice for yeasts isolated from tequila and mezcal than compared to the bakery yeast.