Flavor encapsulation in yeasts: limonene used as a model system for characterization of the release mechanism

Sonoprocessing enhances the stabilization of fisetin by encapsulation in Saccharomyces cerevisiae cells

The objective of this study was to investigate for the first time the role of S. cerevisiae natural barriers and endogenous cytoplasmatic bodies on the stabilization of fisetin encapsulated via sonoprocessing coupled to freeze-drying (FD) or spray drying (SD). Both protocols of encapsulation improved the resistance of fisetin against thermal treatments (between 60 and 150 °C) and photochemical-induced deterioration (light exposition for 60 days) compared to non-encapsulated fisetin (antioxidant activity retention of approximately 55% and 90%, respectively). When stored under constant relative humidity (from 32.8 to 90%) for 60 days, yeast carriers improved the half-life time of fisetin by up to 4-fold. Spray dried particles were smaller (4.9 μm) and showed higher fisetin release after simulated gastrointestinal digestion (55.7%) when compared to FD. Freeze-dried particles, in turn, tended to agglomerate more than SD (zeta potential -19.7 mV), resulting in reduced loading features (6.3 mg/g) and less efficient protection of fisetin to heat, photo, and moisture-induced deterioration. Overall, spray-dried sonoprocessed fisetin capsules are an efficient way to preserve fisetin against harsh conditions. Altogether, this report shows that sonoprocessing coupled to drying is an efficient, creative, and straightforward route to protect and deliver lipophilic fisetin using yeast capsules for food applications.

Potential Application of Yeast Cell Wall Biopolymers as Probiotic Encapsulants

Biopolymers of yeast cell walls, such as β-glucan, mannoprotein, and chitin, may serve as viable encapsulants for probiotics. Due to its thermal stability, β-glucan is a suitable cryoprotectant for probiotic microorganisms during freeze-drying. Mannoprotein has been shown to increase the adhesion of probiotic microorganisms to intestinal epithelial cells. Typically, chitin is utilized in the form of its derivatives, particularly chitosan, which is derived via deacetylation. Brewery waste has shown potential as a source of β-glucan that can be optimally extracted through thermolysis and sonication to yield up to 14% β-glucan, which can then be processed with protease and spray drying to achieve utmost purity. While laminarinase and sodium deodecyle sulfate were used to isolate and extract mannoproteins and glucanase was used to purify them, hexadecyltrimethylammonium bromide precipitation was used to improve the amount of purified mannoproteins to 7.25 percent. The maximum chitin yield of 2.4% was attained by continuing the acid-alkali reaction procedure, which was then followed by dialysis and lyophilization. Separation and purification of yeast cell wall biopolymers via diethylaminoethyl (DEAE) anion exchange chromatography can be used to increase the purity of β-glucan, whose purity in turn can also be increased using concanavalin-A chromatography based on the glucan/mannan ratio. In the meantime, mannoproteins can be purified via affinity chromatography that can be combined with zymolase treatment. Then, dialysis can be continued to obtain chitin with high purity. β-glucans, mannoproteins, and chitosan-derived yeast cell walls have been shown to promote the survival of probiotic microorganisms in the digestive tract. In addition, the prebiotic activity of β-glucans and mannoproteins can combine with microorganisms to form synbiotics.

Physicochemical and Morphological Study of the Saccharomyces cerevisiae Cell-Based Microcapsules with Novel Cold-Pressed Oil Blends

Vegetable oils rich in polyunsaturated fatty acids are a valuable component of the human diet. Properly composed oil blends are characterized by a 5:1 ratio of ω6/ω3 fatty acids, which is favorable from a nutritional point of view. Unfortunately, their composition makes them difficult to use in food production, as they are susceptible to oxidation and are often characterized by a strong smell. Encapsulation in yeast cells is a possible solution to these problems. This paper is a report on the use of native and autolyzed yeast in the encapsulation of oils. The fatty acid profile, encapsulation efficiency, morphology of the capsules obtained, and thermal behavior were assessed. Fourier transform infrared analysis and low-field nuclear magnetic resonance relaxation time measurements were also performed. The process of yeast autolysis changed the structure of the yeast cell membranes and improved the loading capacity. Lower encapsulation yield was recorded for capsules made from native yeast; the autolysis process significantly increased the value of this parameter. It was observed that NY-based YBMCs are characterized by a high degree of aggregation, which may adversely affect their stability. The average size of the AY capsules for each of the three oil blends was two times smaller than the NY-based capsules. The encapsulation of oils in yeast cells, especially those subjected to the autolysis process, ensured better oxidative stability, as determined by DSC, compared to fresh blends of vegetable oils. From LF NMR analysis of the relaxation times, it was shown that the encapsulation process affects both spin-lattice T1 and spin-spin T2* relaxation times. The T1 time values of the YBMCs decreased relative to the yeast empty cells, and the T2* time was significantly extended. On the basis of the obtained results, it has been proven that highly unsaturated oils can be used as an ingredient in the preparation of functional food via protection through yeast cell encapsulation.

Efficient encapsulation of curcumin into spent brewer's yeast using a pH-driven method

Curcumin (CUR) was encapsulated into yeast cells (YCs) through a pH-driven method with a 5.04-fold increase in loading capacity and a 43.63-fold reduction in incubation time compared to the conventional diffusion method. Optimal encapsulation was obtained when the mass ratio of CUR to YCs was 0.1, and the loading capacity and encapsulation efficiency were 8.07% and 80.66%, respectively. Encapsulation of CUR into YCs was confirmed by fluorescence microscopy, differential scanning calorimetry, and thermogravimetric analysis. Fourier transform infrared spectroscopy and X-ray diffraction further demonstrated that the encapsulated CUR was interacted with mannoprotein and β-glucan of the cell wall network through hydrophobic interaction and hydrogen bond in amorphous state. The in vitro bioaccessibility of YCs-loaded CUR was significantly increased by 6.05-fold. The enhanced encapsulation efficiency and rapid encapsulation process proposed in this study could facilitate YCs-based microcarriers to encapsulate bioactive substances with higher bioaccessibility.

Microencapsulation of Hibiscus sabdariffa L. Calyx Anthocyanins with Yeast Hulls

Yeast hulls, due to their specific thin mannoprotein layer and high content of β-glucan, constitute a promising material to stabilise the colour of anthocyanins. This study evaluates the potential of yeast hulls on the freeze-drying encapsulation of anthocyanins-rich extract from Hibiscus sabdariffa L. calyx with comparison to maltodextrin microcapsules. The moisture content (5.28-16.38%), water activity (< 0.039-0.307) and hygroscopicity (17.50-25.99 g/100 g) of obtained powders were evaluated. The stability of encapsulated anthocyanins, monitored through the total anthocyanin content, was evaluated with the pH differential method immediately after production and after a 10-week storage under different conditions of temperature (5 or 37 °C), humidity (45 or 85% RH), in presence or absence of light. The colour parameters (a, b*, L*, C*, H°, ΔE^*) of powders were measured. The results indicated that yeast-hulls showed a good ability to protect anthocyanin against the influence of temperature, light, moisture compared to freeze-dried anthocyanins-rich extracts (p < 0.05). Yeast hulls protected anthocyanin better than maltodextrin under high humidity conditions (p < 0.05).

Effects of Saccharomyces cerevisiae cell wall addition on feed digestibility, fecal fermentation and microbiota and immunological parameters in adult cats

Background

This study aimed to evaluate the effects of increasing dosages of a commercial product composed by Saccharomyces cerevisiae yeast (YAM), with active metabolites, which are beta glucans, nucleotides, organic acids, polyphenols, amino acids, vitamins and minerals (Original XPC^tm, Diamond V, IOWA, USA) added to a commercially available dry cat food. Apparent digestibility of dietary nutrients, fecal microbiota, fecal fermentation products and immunological parameters were evaluated. Twenty-seven healthy cats of mixed sexes, with a mean body weight of 4.19 ± 0.83 kg and a mean age of 9.44 ± 5.35 years were distributed by age in an unbalanced randomized block design, consisting of three experimental treatments: CD (control diet), YAM 0.3 (control diet with 0.3% yeast with active metabolites) and YAM 0.6 (control diet with 0.6% yeast with active metabolites).

Results

The inclusion of the additive elevated the apparent digestibility of crude fiber (p = 0.013) and ash (p < 0.001) without interfering feed consumption, fecal production and fecal characteristics. Regarding fermentation products present in the feces, prebiotic inclusion increased lactic acid concentration (p = 0.004) while reducing isovaleric acid (p = 0.014), only in the treatment YAM 0.3. No differences were noticed on biogenic amines (BA), fecal pH, ammonia concentration, total and individuals short-chain fatty acids (SCFA) and total and individuals branched-chain fatty acids (BCFA) (except isovaleric acid in YAM 0.3). As regards to fecal microbiota, prebiotic inclusion has resulted in the reduction of Clostridium perfringens (p = 0.023). No differences were found in the immunological parameters evaluated.

Conclusion

It can be concluded that the additive, at the levels of inclusion assessed shows prebiotic potential and it has effects on fecal fermentation products and microbiota without interfering on crude protein and dry matter digestibility. More studies evaluating grater inclusion levels of the prebiotic are necessary to determine optimal concentration.

Persistence Enhancement of a Promising Tick Repellent, Benzyl Isothiocyanate, by Yeast Microcarriers

Phenethyl isothiocyanate isolated from Armoracia rusticana root oil and its derivatives were tested at different doses in a bioassay designed to evaluate repellency against individual Haemaphysalis longicornis nymphs. Among the tested compounds, benzyl isothiocyanate exhibited repellency against H. longicornis nymphs at the lowest dose of 0.00625 mg/cm², followed by phenethyl isothiocyanate (0.0125 mg/cm²) and phenyl isothiocyanate (0.025 mg/cm²). The behavioral responses of H. longicornis nymphs exposed to benzyl isothiocyanate and phenethyl isothiocyanate indicated that the mode of action of these compounds can be mainly attributed to the vapor phase. Encapsulated benzyl isothiocyanate showed repellency up to 120 min post-application at 0.1 mg/cm², whereas pure benzyl isothiocyanate showed repellency up to 60 min post-application at 0.1 mg/cm². The present study suggests that benzyl isothiocyanate is a potential repellent for protection against H. longicornis nymphs, and encapsulation in yeast cells may enhance the repellency effect.

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.

Anticancer activity of limonene: A systematic review of target signaling pathways

Limonene (LIM) is a monoterpene, which is abundant in essential oils of Citrus fruits peels (Rutaceae). More recently, LIM, as a potential natural anticancer compound, has attracted major attention and exerted a chemopreventive activity, stimulating the detoxification of carcinogenic compounds and limiting tumor growth and angiogenesis in various cancer models. Twenty-six (26) articles were selected based on previously established criteria. Anticancer activity of LIM was related to the inhibition of tumor initiation, growth, and angiogenesis and the induction of cancer cells apoptosis. LIM was able to increase Bax expression, release cytochrome c, and activate the caspase pathway. In addition, LIM increased the expression of p53 and decreased the activity of Ras/Raf/MEK/ERK and PI3K/Akt pathways. LIM also decreased the expression of VEGF and increased the activities of the Man-6-P / IGF2R and TGF-βIIR receptors. These results highlight LIM as an abundant natural molecule with low toxicity and pleiotropic pharmacological activity in cancer cells, targeting various cell-signaling pathways critically involved in the initiation, growth, and chemoresistance of cancer cells.

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.

Saccharomyces cerevisiae as a delivery system of Zataria multiflora Boiss. essential oil as a natural preservative for food applications: Encapsulation of Iranian Zataria multiflora Boiss. essential oil

BACKGROUND

The following study is an evaluation of the encapsulation, stability and release profile of Iranian Zateria multiflora boiss essential oil (ZEO) in Saccharomyces cerevisiae yeast cells. Encapsulation was performed with different essential oil / yeast weight ratios at different temperatures. The encapsulation efficiency and stability of the loaded yeasts and the release profiles of carvacrol and thymol (as the main active ingredients of ZEO) were also investigated.

RESULT

The encapsulation efficiencies of carvacrol and thymol at a ZEO / yeast weight ratio of 1.25 were 30.9% ± 0.01% and 44.5% ± 0.02%, respectively. Loaded yeast cells were stable during the 4-week storage period. Both carvacrol and thymol showed substantial releases of around 60% during the first hour and around 70% during the second hour at two different water temperatures, followed by steady release.

CONCLUSION

Zateria multiflora boiss essential oil can be encapsulated effectively in S. cerevisiae yeast cells, refrigerated without degradation, and released efficiently. Zateria multiflora boiss essential oil encapsulated into S. cerevisiae yeast may be used as a potential preservative for the food and drug industry. © 2020 Society of Chemical Industry.

Biobased Materials from Microbial Biomass and Its Derivatives

There is a strong public concern about plastic waste, which promotes the development of new biobased materials. The benefit of using microbial biomass for new developments is that it is a completely renewable source of polymers, which is not limited to climate conditions or may cause deforestation, as biopolymers come from vegetal biomass. The present review is focused on the use of microbial biomass and its derivatives as sources of biopolymers to form new materials. Yeast and fungal biomass are low-cost and abundant sources of biopolymers with high promising properties for the development of biodegradable materials, while milk and water kefir grains, composed by kefiran and dextran, respectively, produce films with very good optical and mechanical properties. The reasons for considering microbial cellulose as an attractive biobased material are the conformational structure and enhanced properties compared to plant cellulose. Kombucha tea, a probiotic fermented sparkling beverage, produces a floating membrane that has been identified as bacterial cellulose as a side stream during this fermentation. The results shown in this review demonstrated the good performance of microbial biomass to form new materials, with enhanced functional properties for different applications.

Encapsulation of Mentha pulegium Essential Oil in Yeast Cell Microcarriers: An Approach to Environmentally Friendly Pesticides

A green approach for the encapsulation of Mentha pulegium essential oil in commercial baker's yeast and its evaluation as a pesticide against the insect pest Myzus persicae are presented. Upon treating aqueous yeast cell dispersion with the essential oil, the formation of essential-oil-loaded microparticles of about 9 μm is observed, with a loading capacity ranging from 29 to 36%, depending upon the encapsulation conditions. The thermal properties of the microparticles were characterized using differential scanning calorimetry and thermogravimetric analysis, confirming the protection of the essential oil from the cells. Encapsulation prolonged the insecticidal activity of the essential oil by 3 days.

Repellent Effects of Encapsulated Carvacrol on the Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Rhipicephalus (Boophilus) microplus (Canestrini) is a problem for livestock production systems, and its control has become challenging due to the selection of tick populations resistant to synthetic chemical acaricides. The use of repellent compounds prevents contact between the arthropod parasite and the host and can, thus, contribute to increases in the efficacy of these acaricides. Carvacrol monoterpenic phenol is a possible alternative method for controlling R. (B.) microplus; however, this compound is highly volatile, and its volatilization can be decreased through microencapsulation, which results in the timed release of the compound. The cell wall of Saccharomyces cerevisiae can be utilized for the protection of volatile molecules. The aim of this study was to evaluate the in vitro repellent effect of yeast cell wall-encapsulated carvacrol on susceptible R. (B.) microplus larvae. Specifically, the vertical filter paper bioassay was employed to analyze the repellent activity of encapsulated carvacrol, nonencapsulated carvacrol, and N,N-diethyl-meta-toluamide at concentrations ranging from 0.75 to 0.001 mg/cm2, and the repellent activities were evaluated. Both carvacrol and encapsulated carvacrol exhibited repellent effects on R. (B.) microplus larvae, and the encapsulated compound showed the highest repellent activities at the lowest concentrations. Carvacrol encapsulated exhibited a low repellent concentration in all times (≤0.05 mg/cm2), whereas the carvacrol nonencapsulated ranged CR50 from 0.13 to 0.27 mg/cm2 at 1- to 6-h posttreatment. The present paper provides the first description of the use of a microencapsulation technique for achieving the highest repellent effect of carvacrol and indicates that this technique might be used to obtain new delivery systems for volatile and hydrophobic compounds.

Kinetic study of controlled release of flavor compounds from spray-dried encapsulated yeast powder using dynamic vapor sorption–gas chromatography

The release profile of d-limonene and ethyl hexanoate was investigated using a dynamic vapor sorption (DVS) system coupled with gas chromatography. The flavors were encapsulated by spray drying using Saccharomyces cerevisiae cells from which β-glucan had been partially extracted. Relative humidity (RH) was stepped from 20% to 50, 60, 70, and 80% at 30, 40, 50, and 60ºC. The maximum release flux for d-limonene and ethyl hexanoate was around 12 and 28 mg/s∙m2∙g-powder at 80% RH and 60ºC incubation. The Weibull distribution function was well fitted with the experimental data to analyze release kinetics. The release mechanism parameter was greater than 1.0, which indicates a controlled release with initial induction time. The activation energy for ethyl hexanoate (6 kJ/mol) was lower than d-limonene (41 kJ/mol) at 80% RH, which indicates higher affinition of ethyl hexanoate to migrate from the lipid bilayer membrane towards the water phase.

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.

The cell wall compound of Saccharomyces cerevisiae as a novel wall material for encapsulation of probiotics

Yeast cell wall is known as a food grade ingredient which is recently being used increasingly as a novel coating for encapsulation of different materials in the food industry. This application is limited to core materials smaller than yeast in size. In this study, we have tried to encapsulate larger particles by crushing yeast cells. Hence, probiotic bacteria of Lactobacillus acidophilus and Bifidobacterium bifidum were encapsulated firstly by calcium alginate using the emulsion method and these microbeads were coated again by Saccharomyces cerevisiae cell wall compound and another layer of calcium alginate. The average diameter of microcapsules for single layer microbeads (M), microbeads coated by two layers of alginate (MCA), and microbeads coated by a layer of yeast cell and two layers of alginate (MCYA) were 54.25±0.18, 77.43±8.24 and 103.66±13.33μm, respectively. In simulated gastrointestinal conditions, there was a significant (P<0.05) enhancement in resistance of L. acidophilus when applying a layer of S. cerevisiae cell wall compound. For MCA and MCYA after 2h exposure to simulated gastric juice, it was revealed a log reduction of 1.53±0.1 and 1.1±0.02 with pH1.55 and in simulated intestinal juice, 2.92±0.04 and 2.42±0.06 with 0.6% bile after previous 1h incubation in gastric conditions, respectively. It can be concluded that the cell wall compound of S. cerevisiae is a suitable protective coating for probiotics and it can improve the survival of probiotics within food products.

Molecule structural factors influencing the loading of flavoring compounds in a natural-preformed capsule: Yeast cells

Yeast cells are efficient microcapsules for the encapsulation of flavoring compounds. However, as they are preformed capsules, they have to be loaded with the active. Encapsulation efficiency is to a certain level correlated with LogP. In this study, the effect of structural factors on the encapsulation of amphiphilic flavors was investigated. Homological series of carboxylic acids, ethyl esters, lactones, alcohols and ketones were encapsulated into the yeast Yarrowia lipolytica. Although, in a single homological series, the length of the molecule and thus the LogP were correlated with encapsulation efficiency (EY%), big differences were observable between series. For instance, carboxylic acids and lactones exhibited EY% around 45%-55%, respectively, for compounds bigger than C8 and C6, respectively, whereas ethyl esters reached only about 15-20% for C10 compounds. For a group of various C6-compounds, EY% varied from 4% for hexanal to 45% for hexanoic acid although the LogP of the two compounds was almost similar at 1.9. In total our results point out the importance of the level of polarity and localization of the polar part of the compound in addition to the global hydrophobicity of the molecule. They will be of importance to optimize the encapsulation of mixtures of compounds.

Chemical treatment and chitosan coating of yeast cells to improve the encapsulation and controlled release of bovine serum albumin

We investigate the encapsulation of bovine serum albumin (BSA) in chemical-treated and chitosan-coated yeast cells, Saccharomyces cerevisiae (S. cerevisiae), for the controlled release of BSA. The chemical treatment can sufficiently enlarge the small-sized cell-wall cavities and/or break the integrity for the entrance of BSA to the interior of yeast cells, and the additional chitosan coating can well prevent the rapid release of encapsulated BSA from the yeast-derived microcapsules. The sodium hydroxide pretreated S. cerevisiae gives a maximum encapsulation yield of (10.1 ± 0.2)% for BSA. An additional coating of S. cerevisiae with chitosan can reduce the initial burst release of BSA and extend the release period from 24 h in the chitosan-free case to 48 h in phosphate buffer at pH 7.4. The prepared microcapsules can well keep the shapes and sizes of yeast cells and thus show uniform sizes of 3.85 ± 0.81 μm. The encapsulated BSA well retains its pristine ultraviolet spectroscopic and chromatographic behaviors. The present microencapsulation protocol has the advantages of convenient and mild operation, high encapsulation efficiency, and organic solvent-free nature, which is of reference value for establishing high-performance controllable biomacromolecule-delivery systems.

Sorption of grape proanthocyanidins and wine polyphenols by yeasts, inactivated yeasts, and yeast cell walls

Inactivated yeast fractions (IYFs) can be used in enology to improve the stability and mouthfeel of red wines. However, information concerning the mechanisms involved and the impact of the IYF characteristics is scarce. Adsorption isotherms were used to investigate interactions between grape proanthocyanidin fractions (PAs) or wine polyphenols (WP) and a commercial yeast strain (Y), the inactivated yeast (IY), the yeast submitted to autolyzis and inactivation (A-IY), and the cell walls obtained by mechanical disruption (CW). High affinity isotherms and high adsorption capacities were observed for grape PAs and whole cells (Y, IY, and A-IY). Affinity and adsorbed amount were lower with wine PAs, due to chemical changes occurring during winemaking. By contrast to whole cells, grape PAs and WP adsorption on CW remained very low. This raises the issue of the part played by cell walls in the interactions between yeast and proanthocyanidins and suggests the passage of the latter through the wall pores and their interaction with the plasma membrane.

Microorganism-based monodisperse microcapsules: encapsulation of the fungicide tebuconazole and its controlled release properties

A controlled release system was prepared, it based on UF modified PCC cells in which TEB are loaded into cells. It can control the drug release rate, depress the initial “burst effect”, and was efficacious in controlling wheat powdery mildew.

Osmoporation: a simple way to internalize hydrophilic molecules into yeast

Internalization of hydrophilic molecules into yeast cytosol is required for different applications such as cell transformation or preservation of water soluble components by bioencapsulation. However, these molecules are not able to cross the plasma membrane and strategies have to be developed. Recent works revealed that osmotic perturbations could induce non-lethal transient permeabilization of the plasma membrane. In this work, we endeavored to clarify the phenomenon of permeabilization during rehydration after a mild hyperosmotic perturbation in order to evaluate the possibility of hydrophilic molecule internalization in yeast by this treatment. Rehydration step is particularly interesting because the large entry of water into the cells could help the internalization of molecules. The internalization of a fluorescent molecule [fluorescein isothiocyanate Dextran (FITC-Dextran), 20 kDa], added during the rehydration after a sublethal hyperosmotic treatment, was studied in Saccharomyces cerevisiae yeast cells. The internalization kinetic and the localization of the fluorescent molecules were studied by flow cytometry and fluorescence confocal microscopy. Our results show that the rehydration leads to the rapid internalization of FITC-Dextran due to a transient plasma membrane permeabilization. Thus, osmoporation, i.e. plasma membrane poration by modifications of osmotic pressure of the extracellular medium, could be a new and simple way to deliver molecules of particular interest into yeasts.

Yeast cells as microcapsules. Analytical tools and process variables in the encapsulation of hydrophobes in S. cerevisiae

Yeast cells can be used as biocompatible and biodegradable containers for the microencapsulation of a variety of actives. Despite the wide application of this process, e.g. in the food industry, mechanism and controlling factors are yet poorly known. In this study we have studied kinetics and mechanistic aspects of the spontaneous internalization of terpenes (as model hydrophobic compounds) in Saccharomyces cerevisiae, quantifying their encapsulation through HPLC analysis and fluorescent staining of lipidic bodies with Nile Red, while in parallel monitoring cell viability. Our results showed that this encapsulation process is essentially a phenomenon of passive diffusion with negligible relevance of active transport. Further, our evidence shows that the major determinant of the encapsulation kinetics is the solubility of the hydrophobe in the cell wall, which is inversely related to partition coefficient (log P).