Non-dialyzable Fractions Research Articles

Method Validation for Multi-Elemental Analysis of Dialyzable and Non-dialyzable Fractions of Coffee Brews by F AAS and ICP OES: a Bioaccessibility Study

A simple and fast, non-digestion treatment, and fully validated preparation procedures of dialyzable and non-dialyzable fractions of brews of ground (GCs) and instant (ICs) coffees prior to their elemental analysis (Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Sr, and Zn) by flame atomic absorption spectrometry (F AAS) and inductively coupled plasma optical emission spectrometry (ICP OES) was developed. Three different procedures: wet digestions (P1), direct analysis (P2), and acidification with HNO3 (P3) were tested. Among tested procedures, the direct analysis (P2) gave the most satisfactory results, i.e., precision from 0.54% (Fe) to 5.9% (Cu), recoveries ranging between 98.0% (Sr) and 104% (Al), detection limits within 0.095 (Ba)–1.8 (Ni) μg L−1, and quantification limits from 0.32 (Ba) to 6.0 (Ni) μg L−1. The chosen procedure was applied to determine bioaccessibility of 11 elements in GCs and ICs coffees using in vitro gastrointestinal digestion. Average contributions of the bioaccessible fraction (%) of elements in brews were as follows: Al (19.0, 23.0), Ba (42.8, 48.4), Ca (35.0, 38.9), Cr (< LOD, 31.1), Cu (15.0, 14.3), Fe (5.08, 2.81), Mg (32.2, 37.9), Mn (28.1, 29.1), Ni (40.9, 60.0), Sr (43.2, 45.6), and Zn (11.5, 9.57) for GCs and ICs coffees, respectively. Generally, bioaccessibility of most elements, i.e., Al, Ba, Ca, Cu, Mg, Mn, Ni, and Sr in brews of GCs was lower than this determined in ICs and varied from 4% (Mn) to 47% (Ni). In contrast, higher contributions of the bioaccessible fraction of Fe and Zn were assessed for GCs brews (47% and 17%, respectively), than these evaluated in ICs brews. Additionally, results on total concentrations of elements in brews of GCs and ICs and concentrations of elements in the dialyzable fraction separated from these brews were applicable to differentiate and classify all analyzed coffees by principal component analysis (PCA).

Investigating the effects of food matrix and food components on bioaccessibility of pomegranate (Punica granatum) phenolics and anthocyanins using an in-vitro gastrointestinal digestion model

Effects of food matrix and individual food components on potential bioaccessibility of pomegranate were investigated by means of simulating in vitro gastrointestinal (GI) digestion. The foodstuffs (sunflower oil, skim milk, cooked lean meat, bread, skim yogurt, probiotic yogurt, apple, lemon, honey, soy milk, cream, and soybean) and the food components (gluten, casein, isolated meat protein, lactose, fructose, galactose, glucose, salt, ascorbic acid, starch, cooked starch, tocopherol, linoleic acid, cellulose, citric acid and pectin) were codigested with pomegranate in model systems to better understand matrix effects. Total phenolic content (TPC) and total anthocyanin content (TAC) were determined by spectrophotometric methods and major phenolics/anthocyanins were analyzed by RP-HPLC/PDA detection both before and after in vitro GI digestion at post gastric (PG), dialyzable (IN) and non-dialyzable (OUT) fractions. Phenolics of pomegranate were found to be stable during gastric conditions (115%), with 25% loss in pancreatic digestion, available (14%) in IN. Although preserved (89%) in PG, anthocyanins were lost in pancreatic digestion (38%), but still available (12%) in IN. Milk, bread, yogurt, probiotic yogurt, lactose, starch, cellulose, salt, citric acid or tocopherol codigestion with pomegranate decreased TPC for all fractions. Proteins affected losses in PG and OUT fractions. Carbohydrates such as starch, lactose, glucose and pectin appeared to affect the loss of phenolics and exerted 2-fold decreases in serum fraction (IN). For TAC, only meat, soymilk or cream codigestion with pomegranate resulted in IN losses. Proteins did not significantly affect TAC in IN, but were inhibitory in PG. However, carbohydrates and fatty acids significantly increased TAC in IN. Generally cyanidins were found to be more stable in food matrices and pancreatic conditions than other anthocyanins.

In vitro bioavailability of total selenium and selenium species from seafood

In vitro bioavailability of total selenium and selenium species from different raw seafood has been assessed by using a simulated gastric and intestinal digestion/dialysis method. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to assess total selenium contents after a microwave assisted acid digestion, and also to quantify total selenium in the dialyzable and non-dialyzable fractions. Selenium speciation in the dialyzates was assessed by high performance liquid chromatography (HPLC) coupled with ICP-MS detection. Major Se species (selenium methionine and oxidized selenium methionine) from dialyzate were identified and characterized by HPLC coupled to mass spectrometry (HPLC–MS). Selenocystine was detected at low concentrations while Se-(Methyl)selenocysteine and inorganic selenium species (selenite and selenate) were not detected in the dialyzate. Low bioavailability percentages for total selenium (6.69±3.39 and 5.45±2.44% for fish and mollusk samples, respectively) were obtained. Similar bioavailability percentages was achieved for total selenium as a sum of selenium species (selenocystine plus oxidized selenium methionine and selenium methionine, mainly). HPLC–MS data confirmed SeMet oxidation during the in vitro procedure.

Assessment of the bioavailability of toxic and non-toxic arsenic species in seafood samples

Bioavailability of total arsenic, toxic (arsenite, As(III); and arsenate, As(V)), and non-toxic (monomethylarsonic acid, MA; dimethylarsonic acid, DMA; arsenobetaine, AB; and arsenocholine, AC) arsenic species has been assessed in different raw seafood samples (white fish, cold water fish and molluscs) by using an in vitro model that combines simulated gastric and intestinal digestion/dialysis methods. Correlations between arsenic species bioavailability and seafood nutrient contents (fat and protein) have also been established. Total arsenic content in seafood samples, and dialyzable and non-dialyzable fractions, were analyzed by inductively coupled plasma – mass spectrometry (ICP–MS) after a microwave-assisted acid digestion treatment. The determination of the different arsenic species concentrations in the samples (after an optimised matrix solid phase dispersion (MSPD) approach) and in the dialyzable fraction was done by high performance liquid chromatography (HPLC) coupled to ICP-MS as a selective detector. Accuracy of the procedure (total arsenic determination) was assessed by analyzing DORM-2 and BCR-627 certified reference materials. The accuracy of the in vitro procedure was established through a mass-balance study. After statistical evaluation (95% confidence interval), good accuracy of the whole in vitro process, for total arsenic and for arsenic speciation, was observed. High dialyzability percentages for total arsenic and for arsenic species were found (i.e. from 84.6±1.7% to 106±2.6%). Bioavailability of arsenic exhibits a negative correlation with the fat content of the seafood. However, no correlation was observed between the bioavailable fraction of total arsenic and arsenic species and the protein content of the seafood studied.

Bioavailability study using an in-vitro method of iodine and bromine in edible seaweed

Raw edible seaweed harvested in the Galician coast (Northwester Spain), including two red seaweed types (Dulse and Nori), three brown seaweed (Kombu, Wakame and Sea Spaghetti), one green seaweed (Sea Lettuce) and one microalgae ( Spirulina platensis) were analysed for total iodine and total bromine, as well as for iodine and bromine bioavailability by in-vitro methods (simulated gastric and intestinal digestion/dialysis). Similarly, a cooked seaweed sample (canned in brine) consisting of a mixture of two brown seaweed (Sea Spaghetti and Furbelows) and a derived product (agar–agar) from the red seaweed Gelidiumm sesquipedale, were also included in the study. All measurements were carried out by inductively coupled plasma–mass spectrometry using tellurium and yttrium as internal standards for iodine and bromine, respectively. An optimised microwave assisted alkaline (TMAH) digestion procedure was used as sample pre-treatment for total iodine and bromine determinations, as well as for the determination of both elements in the non-dialyzable fractions. PIPES buffer solution at a pH of 7.0 and dialysis membranes of 10 kDa molecular weight cut off (MWCO) were used for the intestinal digestion. Accuracy of the method (total bromine and iodine determinations) was assessed by analysing a NIES-09 certified reference material. The accuracy of the in-vitro procedure was established by a mass-balance study which led, after statistical evaluation (95% confidence interval), good accuracy of the whole in-vitro process. The highest dialyzability bromine percentages (36 ± 0.7% and 47 ± 3.0%) were obtained for red seaweed (Dulse and Nori), while higher dialyzability iodine was assessed for the brown seaweed (Kombu), around 17% ± 0.7%.

Evaluation of an in vitro method to estimate trace elements bioavailability in edible seaweeds

Raw edible seaweed harvested in the Galician coast (Northwestern Spain), including two red seaweed types (Dulse and Nori), three brown seaweed (Kombu, Wakame and Sea Spaghetti), one green seaweed (Sea Lettuce) and one microalgae ( Spirulina platensis) were studied to assess trace elements bioavailability using an in vitro method (simulated gastric and intestinal digestion/dialysis). Similarly, a cooked seaweed sample (canned in brine) consisting of a mixture of two brown seaweed (Sea Spaghetti and Furbelows) and a derived product (Agar–Agar) from the red seaweed Gelidiumm sesquipedale, were also included in the study. The total trace element content as well as the non-dialyzable fractions was carried out after a microwave acid digestion of the seaweed samples by inductively coupled plasma-mass spectrometry (ICP-MS). The dialyzable fraction was determined without any pre-treatment by ICP-MS. PIPES buffer solution at a pH of 7.0 and dialysis membranes of 10 kDa molecular weight cut off (MWCO) were used for intestinal digestion. Accuracy of the method was assessed by analyzing a NIES-09 certified reference material ( Sargasso seaweed). The accuracy of the in vitro procedure was established by a mass balance study which led to good accuracy of the whole in vitro process, after statistical evaluation (95% confidence interval). The highest dialyzability percentages (100 ± 0.2%) were obtained for Dulse in Mn and V.

Oxidative activity and dialyzability of some iron compounds under conditions of a simulated gastrointestinal digestion in the presence of phytate

The oxidative activity of some iron compounds was compared under conditions of gastrointestinal digestion and correlated with iron solubility and dialyzability. Ferric chloride, NaFeEDTA, ferrous bis-glycinate, ferrous gluconate, or ferrous lactate, were mixed with water or a phytate solution or a phytate solution treated with phytase and digested in vitro. The dialyzable and the non-dialyzable fractions of the digests were analyzed for oxidative activity on linoleic acid liposomes and iron solubility and dialyzability. In all dialyzable and non-dialyzable fractions, oxidative activity was variable in water ( P < 0.05), lower and similar for all iron compounds in phytate ( P < 0.05), higher and variable in phytate solutions treated with phytase ( P < 0.05). In most digests, ferric chloride was least active, followed by ferrous lactate, NaFeEDTA and ferrous bis-glycinate. There was no correlation between oxidative activity and iron dialyzability or solubility. These results point to variable oxidative properties that iron compounds may potentially exhibit in the lumen.

Architecture of alkaline-soluble and bioactive polysaccharide from the kernels of Prunus mume Sieb. et Zucc. assessed by anti P-1 antibody.

P-1 was partially hydrolyzed with 0.01, 0.05, and 0.1 M trifluoroacetic acid (TFA), successively, and the dialyzable (E-1, E-2, and E-3) and non-dialyzable (I-1, I-2, and I-3) fractions were prepared and analyzed chemically and immunochemically. Either I-1 or E-1 reacted with anti P-1 serum as strongly as P-1 and were mitogenic. The cross-reactivity of I-2 and I-3 was less than I-1 with anti P-1 serum. However, they were as mitogenic as I-1. The cross-reactivity of E-2 and E-3 to anti P-1 serum was also very weak, and they were not mitogenic. The E-1 fraction had a similar sugar composition to I-1 and P-1. E-2 was a monosaccharide, all of Ara, and would be from the linkage of furanosyl residues in P-1. The composition of E-3 was free from Ara and the structure of E-3 was similar to that of I-3. E-3 would be considered to be deleted arabinofuranose from E-1. These results suggest that the mitogenic activity measured by the alkaline phosphatase assay is a property of the core part, I-3, but that P-1 contains several epitopes other than the core part by the immunochemical analysis.

Binding of Todd-Hewitt broth antigens by Streptococcus mutans

Streptococcus mutans 10449, grown in chemically defined culture medium, was tested for its ability to bind 3H-labeled Todd-Hewitt broth components (greater than 12,000 Mr). Maximum adsorption of radioactivity occurred within 5 min at room temperature, and cell-bound material was not completely removed by extended washing with buffer. Heat-killed, arsenate-inhibited, and viable bacteria bound similar quantities. Only 0.09% of the radioactivity in the preparation of high Mr Todd-Hewitt broth components was removed by absorption with excess numbers of S. mutans 10449 cells. Binding followed saturation kinetics and was competitively inhibited by unlabeled medium components, both the dialyzable and nondialyzable fractions. Other oral streptococci were also found to bind these complex medium components. Rabbit antiserum elicited to the high-molecular-weight Todd-Hewitt broth components reacted with monkey cardiac muscle and with S. mutans coated with medium components. Absorption of the anti-Todd-Hewitt broth serum with homogenized heart removed antibodies that reacted with Todd-Hewitt broth-coated S. mutans. Therefore, the tissue-specific antigens of this beef heart infusion medium that adsorb to S. mutans can interfere with the detection and characterization of antigens shared by these bacteria and animal tissues.

Determination of water “bound” by soluble subcellular components during low-temperature acclimation in the gall fly larva, Eurosta solidagensis

1. 1. The water of hydration, or bound water, associated with soluble subcellular components was estimated using a microbalance drying technique and correlated with acclimation temperature in the overwintering, freezing-tolerant larva of the goldenrod gall fly, Eurosta solidagensis. 2. 2. Total water bound by soluble components of E. solidagensis increased as the temperature of acclimation decreased from 0.193 g/g dry wt in larvae acclimated to 22 °C to a maximum of 0.633 g/g dry wt in larvae acclimated to −30 °C. 3. 3. Using dialysis (membrane molecular weight cutoff = 12,000 daltons), low-molecular-weight, “dialyzable” components were separated from high-molecular-weight “nondialyzable” soluble components. Both fractions were found to contribute to the increase in water bound with decreased acclimation temperature. The increase was 2.5-fold for the nondialyzable fraction and four fold for the dialyzable fraction between 22 and −30 °C. 4. 4. Total water bound increased as a function of time at a constant acclimation temperature, and this increase was found to be due solely to an increase in water bound by the nondialyzable fraction. 5. 5. The molecular basis of water binding by both the dialyzable and nondialyzable fractions of E. solidagensis is discussed and the role of bound water as a mechanism of overwintering freezing-tolerance is evaluated.

Studies on Alternaria allergens. I. Isolation of allergens from Alternaria tenuis and Alternaria solani.

Extracts of Alternaria tenuis and Alternaria solani were separated into dialyzable (molecular weight less than 10,000) and non-dialyzable forms. The latter was further fractionated by gel filtration through Sephadex G-100 followed by ion-exchange chromatography on DEAE-cellulose. The dialyzable material was fractionated by gel filtration through Sephadex G-50. The allergenic activities of the fractions obtained from the A. tenuis extract was measured in vitro by the radioallergosorbent test assay and the allergenic potency was measured by radioallergosorbent test inhibition assay. Allergenic activity was detected in most of the non-dialyzable fractions, the majority of the activity being in the last G-100 fraction (MW approximately 20,000) which was predominantly protein in nature. The same component may be responsible for the activity found in the dialyzate and its first G-50 fraction since the immunodiffusion studies indicated that the last G-100 fraction has antigenic components in common with those of the first G-50 fraction. In addition, cross-reactions between A. tenuis and A. solani extracts show that the two species share common antigenic determinants.

Purification and characterization of allergens from Parietaria officinalis pollen

The aqueous extract of Parietaria officinalis pollen has been fractionated by ammonium sulphate precipitation, gel filtration on Sephadex G-25, chromatography on DE 52, dialysis, and gel filtration on Sephadex G-75. The allergenic activity, determined with skin test, was recovered both in the dialyzable (D1. D2, D3, D4) and non-dialyzable (ND1, ND2, ND3, ND4) fractions. The active fractions, heterogeneous with respect to molecular weight which was in the range of 12,000–41,000 daltons, shared common properties: they were glycoproteins and precipitated rabbit antiserum: the allergenic activity was resistant to heating at 100°C for 2 hr and to digestion with neuraminidase, while it was destroyed by extensive pronase digestion. Isoelectric points were between 4.6 and 6.4. The spectra of fluorescence emission and of u.v. absorption were determined. Carbohydrate content was 4.9% and 6.7% respectively for dialyzable (D) and non-dialyzable (ND) fractions. A fraction with higher molecular weight, precipitating antiserum but inactive with skin test, was also recovered. We suggest that these fractions are correlated biochemically, antigenically and in their allergenic properties.

Observations on Free Fatty Acids of Skim Milk

Negligible amounts of free fatty acids with greater than twelve carbon atoms are in the dialysate of skim milk obtained by vacuum dialysis. The 6- through 12-carbon free fatty acids exist in equilibrium between the dialyzable and nondialyzable fractions of skim milk at 23C. The percentage of the 4- through 12-carbon free fatty acids of skim milk in the aqueous phase decreases with increasing molecular weight (av. six determinations: 4 carbon 102.1±10.7%; 6 carbon 93.1±8.6%; 8 carbon 83.6±5.1%; 10 carbon 58.6±7.8%; 10:1 carbon 64.2±5.6%; and 12 carbon 19.6±4.5%).

Inhibition of hydroxyproline synthesis by palladium ions

Palladium ions, administered as PdSO 4, markedly affect the incorporation of l-[3,4- 3H 2] proline into non-dialyzable fractions in 10-day chick embryo cartilage explants with a 55–65% reduction in the concentration range 0.06–0.6 mM. Under these conditions the synthesis of [ 3H]hydroxyproline was nearly completely inhibited. Experiments with prolyl hydroxylase (EC 1.14.11.2) indicated a strong irreversible inhibition of the enzyme with a competition between Fe 2+ and Pd 2+. The K i for the inhibition was 0.02 mM. Pd 2+-treated enzyme remained inactive after extensive dialysis. These studies suggest that Pd 2+ may inhibit collagen synthesis by replacing Fe 2+ in the active site of prolyl hydroxylase and forming strong complexes with the enzyme. These studies also point to a potential mechanism of Pd 2+ toxicity.

Effects of topical glucocorticoid medication on collagen biosynthesis in the dental pulp

The aim of the study was to observe pulpal collagen synthesis in response to trauma and to glucocorticoid medication. The material consisted of 290 rabbit pulps and 76 human premolar pulps. Collagen synthesis was determined by incubating whole pulps in a medium containing [14C]proline, and measuring the formation of [14C]hydroxyproline. The effect of glucocorticoids was studied in vitro using rabbit pulps. Hydrocortisone and dexamethasone inhibited collagen synthesis, whereas prednisolone had no marked effect. Hydrocortisone was found to inhibit the synthesis of [14C]hydroxyproline in neutral salt soluble and insoluble non-dialyzable collagen fractions. [14C]hydroxyproline in the dialyzable fraction was increased, suggesting that hydrocortisone increased collagen degradation. In the human material, premolar pulps were experimentally exposed and then medicated with capping agents. The contralateral teeth were exposed and capped with other capping materials, in some cases they were left as intact controls. The exposure led to an increase in the collagen synthesis as indicated by increased [14C]hydroxyproline formation and elevated protocollagen proline hydroxylase activity in the pulp. This enzyme activity was suppressed in pulps capped with a glucocorticoid paste. In addition, the collagen synthesis rate was lower in pulps treated with another glucocorticoid containing compound, when compared to pulps capped with a calcium hydroxide preparation.

Effects of non-viable measles virus on proliferating human lymphocytes. 2. Characteristics of the suppressive reaction.

We have previously found that &lt;i&gt;in vitro &lt;/i&gt;addition of autoclaved measles virus (AMV) suppressed lymphocyte proliferation. The characteristics of this response were further explored. Proliferation induced by both PHA and PWM was depressed as was &lt;sup&gt;14&lt;/sup&gt;C-amino acid incorporation. AMV present in the medium for only the first 2–4 h of culture lead to prominent suppression. Suppressive activity was found in both dialyzable and non-dialyzable fractions of AMV. No evidence of cytotoxicity was seen by three different measurements.

Excretion of Glycosaminoglycans and Glycoproteins in Normal Human Urine with Age

The non-dialyzable fractions of glycosaminoglycans and glycoproteins obtained from the urine of one hundred healthy Japanese were determined by gravimetric analysis after fractionation with CPC (cetylpyridinium chloride). 1) Although there was a marked variation in the concentration of these fractions, children showed relatively higher values than adults. 2) The amounts of these fractions in 24-hr urine increased with age in children, but remained constant after puberty. 3) The relative amounts of these fractions, expressed as mg/24-hr urine/kg body weight, increased with age in younger children, and then decreased to an almost constant level in adults. 4) Although the daily excretion of these fractions showed a tendency to be larger in males than in females, no significant difference could be found in the relative amounts between them. 5) The ratios of the glycoprotein fraction to the glycosaminoglycan fraction increased with age in younger children, but remained almost constant after puberty. 6) These observations indicated higher metabolic rate of these substances in children than in adults. Moreover, the data of the group 3 (10_??_14 years of age) showed that it might represent the period of transition between child and adult. 7) Certain correlations were found between the relative amounts of the glycoprotein fractions and those of the glycosaminoglycan fractions in the subjects either below or over 15 years of age. The equation of regression suggested that there might be two groups of glycoproteins in urine. One group was thought to contain the metabolites of the ground substance of the connective tissues, whereas the other seemed to consist of serum glycoproteins and/or glycoproteins of somatic fluids without relation to the connective tissues.

In vitro studies with “transfer factor” : II. Transfer of the cell-migration inhibition correlate of delayed hypersensitivity in humans with nondialyzable components of leucocyte lysates from humans sensitized to histoplasmin and coccidioidin

“Nonsensitive” cells from skin-test-negative individuals were incubated with whole cell lysates, nondialyzable and dialyzable fractions of leucocyte lysates obtained from strongly skin test sensitive histoplasmin, and/or coccidioidin sensitive donors and specific antigen. “Nonsensitive” cells incubated with whole cell lysate or nondialyzable fractions of lysate in the presence of specific antigen released a substance (MIF) which specifically inhibited the migration of guinea pig macrophages. Dialyzable fractions from active cell lysates incubated with “nonsensitive” cells and specific antigen did not liberate MIF from “nonsensitive” cells. Cell lysates, nondialyzable fractions, or dialyzable fractions alone, or in combination with nonspecific antigens in the presence of “nonsensitive” cells failed to inhibit the migration of guinea pig macrophages.

Comparison of Lymphocyte Transformation, Inhibition of Macrophage Migration and Skin Tests Using Dialyzable and Nondialyzable Tuberculin Fractions from Mycobacterium Bovis (BCG)

Abstract Nondialyzable and dialyzable fractions prepared from BCG culture filtrates were compared in in vitro and in vivo tests for delayed hypersensitivity. With the non-dialyzable fractions in vivo lymphocyte transformation did not correlate with in vitro inhibition of macrophage migration or skin reactivity. The degree of lymphocyte transformation was correlated with the protein content of the fractions. A carbohydrate-rich fraction did not induce lymphocyte transformation but did induce skin reactivity and inhibition of macrophage migration. Activity of the dialyzable fractions in each of the three tests was dependent on molecular size.

Formation of Dimethyl Sulfide by Propionibacterium shermanii ATCC 9617

As an extension of earlier observations on the ability of Propionibacterium shermanii ATCC 9617 to produce dimethyl sulfide, the quantitative production of this compound was investigated to determine the precursor(s) for dimethyl sulfide formation. Dimethyl sulfide was produced in milk culture at both 8 and 30C. At 30C maximum production was attained in 24 hours, further incubation decreased dimethyl sulfide, apparently due to metabolism by the organism. Although the test organism grew readily in sodium lactate broth, it did not produce dimethyl sulfide. Pyruvate as well as cell-free extracts of Streptococcus cremoris and Leuconostoe citrovorum stimulated growth but not dimethyl sulfide formation. Addition of methionine, cysteine, cystathionine or β-dimethylpropiothetin chloride to the fermentation failed to enhance dimethyl sulfide accumulation.Upon rennet coagulation, the precursor fraction for dimethyl sulfide formation by the test organism was recovered mostly but not exclusively, in the whey fraction. After exhaustive dialysis of whey, the dialysate and nondialyzable fractions supported dimethyl sulfide production. When the dialysate was fractionated by gel filtration, the ability of fractions to support dimethyl sulfide production paralleled the protein elution profile. Addition of precipitated whey protein or α-lactalbumin to milk cultures enhanced dimethyl sulfide production. We conclude that P. shermanii ATCC 9617 produces dimethyl sulfide from sulfur-containing amino acids in peptide linkage.