<Emphasis Type="Italic">α</Emphasis>-Galactosidases production by <Emphasis Type="Italic">Debaryomyces hansenii</Emphasis> UFV-1

Extracellular and intracellular α-galactosidases were produced by yeast Debaryomyces hansenii UFV-1 grown on different media with several carbon sources. D. hansenii grown in YP-medium (1% yeast extract and 2% peptone) presented maximum cell mass (8.45 mg/mL) after 36 h of cultivation, with lactose as carbon source, followed by sucrose, glucose, raffinose, and galactose. Higher extracellular and intracellular α-galactosidases activities were observed at 48 h of D. hansenii cultivation in YPmedium containing galactose (0.97 and 5.27 U/mL) and lactose (1.28 and 4.88 U/mL), supporting the evidence for the model of induction for the yeast GAL/MEL regulon, such as described in Sacharomyces cereviseae.     

Antilisterial Activity of Hops Beta Acids in Broth with or Without Other Antimicrobials

ABSTRACT: Hops beta acids (HBA) are parts of hops flowers used to preserve wort and provide flavor in beer, and are reported as having antimicrobial properties. This study evaluated the antilisterial activity of HBA alone or in combination with other known antimicrobials in a culture broth medium. Listeria monocytogenes (10‐strain mixture) was inoculated (2.6 to 2.8 log CFU/mL) into tryptic soy broth supplemented with 0.6% yeast extract (TSBYE) without (control) or with HBA (0.5 to 5.0 μg/mL), potassium lactate (1.0%), sodium diacetate (0.25%), or acetic acid (0.1%), alone or in combination with HBA (0.5 to 3.0 μg/mL). Survival/growth of the pathogen during storage at 4 °C (35 d), 10 °C (20 d), or 25 °C (2 d) was periodically monitored by spiral plating onto tryptic soy agar plus 0.6% yeast extract. As expected, TSBYE without antimicrobials (control) supported rapid pathogen growth with growth rates of 0.40, 2.88, and 9.58 log CFU/mL/d at 4, 10, and 25 °C, respectively; corresponding Y_end values exceeded 9.0 log CFU/mL at 35, 20, and 2 d storage. HBA used alone (1.0 to 5.0 μg/mL) inhibited growth of L. monocytogenes at all 3 temperatures, with inhibition being more pronounced at higher concentrations and at the lower storage temperature (4 °C). The antilisterial activity of HBA (0.5 to 3.0 μg/mL) was enhanced when combined with sodium diacetate, acetic acid, or potassium lactate, achieving complete inhibition at 4 °C when 3.0 μg/mL HBA were used in combination with each of the above antimicrobials. Overall, HBA exhibited promising antilisterial activity in a broth medium and further studies are needed to investigate its potential antilisterial effects in food products.     

Inhibition of Listeria monocytogenes and Salmonella by Combinations of Oriental Mustard,Malic Acid,and EDTA

The antimicrobial activities of oriental mustard extract alone or combined with malic acid and EDTA were investigated against Salmonella spp. or Listeria monocytogenes at different temperatures. Five strain Salmonella or L. monocytogenes cocktails were separately inoculated in Brain Heart Infusion broth containing 0.5% (w/v) aqueous oriental mustard extract and incubated at 4 °C to 21 °C for 21 d. For inhibitor combination tests, Salmonella Typhimurium 02:8423 and L. monocytogenes 2–243 were individually inoculated in Mueller Hinton broth containing the mustard extract with either or both 0.2% (w/v) malic acid and 0.2% (w/v) EDTA and incubated at 10 °C or 21 °C for 10 to 14 d. Mustard extract inhibited growth of the L. monocytogenes cocktail at 4 °C up to 21 d (2.3 log₁₀ CFU/mL inhibition) or at 10 °C for 7 d (2.4 log₁₀ CFU/mL inhibition). Salmonella spp. viability was slightly, but significantly reduced by mustard extract at 4 °C by 21 d. Although hydrolysis of sinigrin in mustard extract by both pathogens was 2 to 6 times higher at 21 °C than at 4 °C to 10 °C, mustard was not inhibitory at 21 °C, perhaps because of the instability of its hydrolysis product (allyl isothiocyanate). At 21 °C, additive inhibitory effects of mustard extract with EDTA or malic acid led to undetectable levels of S. Typhimurium and L. monocytogenes by 7 d and 10 d, respectively. At 10 °C, S. Typhimurium was similarly susceptible, but combinations of antimicrobials were not more inhibitory to L. monocytogenes than the individual agents.     

Cultural conditions and nutritional components affecting the growth and bacteriocin production of Lactobacillus plantarum KC21

This study was conducted to investigate the effect of cultural conditions and nutritional components on the cell growth and bacteriocin production of Lactobacillus plantarum KC21. In cultures without pH control, the bacteriocin activity of L. plantarum KC21 was higher at 30oC, however, the cell growth rate was higher at 37°C. In MRS broth with an initial pH 6.0, the cell growth was lower, but high bacteriocin levels were recorded than at pH 7.0. The bacteriocin activity was maximal in medium containing 1.0 or 1.5% glucose or 1.0% lactose. Yeast extract (0.25 or 0.5%) added to MRS broth increased the bacteriocin activity, moreover, the bacteriocin in the presence of 1.0 or 3.0% NaCl, 0.5% NH₄PO₄, or 0.25 or 0.5% KH₂PO₄ resulted in the activity of 12,800 BU/mL, but excessively high salts concentration hindered the cell growth and bacteriocin production significantly. Besides 1.0 or 2.0 mM MgSO₄ highly increased the bacteriocin activity without affecting the growth of L. plantarum KC21, and ascorbic acid (1.0 or 3.0 ppm) enhanced the bacteriocin activity up to 2 fold.     

Effect of dimorphic regulation on heterologous glucose oxidase production by Mucor circinelloides

The production of Aspergillus niger glucose oxidase (GOX) and native amylase by the recombinant M. circinelloides KFA199 strain under conditions of dimorphic growth was investigated. The recombinant KFA199 strain was compared to its parental ATCC 1216b strain and a wild‐type CBS 232.29 strain under similar morphology‐controlled conditions. Cultivation in Vogel's medium supplemented with ergosterol/Tween‐80 and sparged with nitrogen gas was most suitable for yeast‐like biomass production under anaerobic conditions. Anaerobic growth was characterized by high levels of ethanol formation and linear growth rates of 0.24–0.05/h, indicating metabolic stress. Subsequent to anaerobic growth, cultures were shifted to aerobic conditions to induce aerobic mycelial growth. GOX produced by the recombinant KFA199 after the shift to aerobic conditions was poorly secreted and accumulated intracellularly to 0.56 U/ml_culture. Amylase production by the KFA199, ATCC12b and CBS 232.29 strains was determined during growth on starch after the shift to aerobic culture. Growth‐associated amylase production by the ATCC 1216b (0.63 U/ml_culture) and wild‐type CBS 232.29 (0.33 U/ml_culture) strains was substantially higher than by the recombinant KFA199 strain (0.07 U/ml_culture), which may be related to the leucine auxotrophy of the transformation host, or genetic changes induced during transformation of the KFA199 strain. Copyright © 2010 John Wiley & Sons, Ltd.     

Factors Contributing to Antilisterial Effects of Raw Egg Albumen

Sensitivity of Listeria monocytogenes strain Scott A and Brie-1 to several factors in raw egg albumen was investigated. A concentration of ca 15% of albumen in trypticase soy broth was listeristatic after 24 hr at 35°C, and listericidal effects were observed at higher concentrations. Supplementation of albumen with iron or biotin did not reverse the inhibition. Preheating of albumen (50–80°C) caused progressive loss of antilisterial effects. Supplementation of broth with lysozyme (>1 mg/mL) produced antilisterial effects that were enhanced at pH 9; conalbumin (>6 mg/mL) suppressed cell growth, while ovomucoid (>2 mg/mL) was inhibitory only at pH 9. Results inferred that antilisterial effects of albumen were caused primarily by lysozyme and were enhanced by ovomucoid, conalbumin, and alkaline pH.     

Antimicrobial effects of onion (<Emphasis Type="Italic">Allium cepa</Emphasis> L.) peel extracts produced via subcritical water extraction against <Emphasis Type="Italic">Bacillus cereus</Emphasis> strains as compared with ethanolic and hot water extraction

In this study, the antimicrobial effects of an onion peel extract prepared using subcritical water extraction (SWE) were assessed for possible development into new bio-functional materials. The extraction temperatures were controlled to 110 and 160°C. At 0.15, 0.3, 0.6, and 1.2 mg extract/mL of broth, the growth inhibition and bactericidal activity of SWE extracts against Bacillus cereus KCCM 40935 and KCCM 11341 were compared with those of ethanol and hot-water extracts. In the case of B. cereus KCCM 40935, it appeared that over 0.6 mg/mL of SWE (110°C) extract exerted a bactericidal effect, and 1.2 mg/mL of SWE (160°C) extract exerted a bacteriostatic effect during culturing, and also that B. cereus KCCM 11341 was more resistant than B. cereus KCCM 40935. Furthermore, our results demonstrated that the death time of 10⁷ CFU/mL of B. cereus KCCM 40935 treated with SWE (110°C) extract at 1.2 mg/mL was 60 min at maximum in 0.8% NaCl. Additionally, the cells damaged by SWE extract were observed with a SEM. It was suggested that an extract of onion peels prepared via SWE (110°C) could be used as a functional biomaterial for the food or pharmaceutical industries.     

Enzymatic cross-linking to improve the handling properties of dough prepared within a normal and reduced NaCl environment

This research examines the use of three enzymes [glucose oxidase (GOX), hexose oxidase (HOX), and xylanase (XYL)] and their combinations [GOX–XYL and HOX–XYL] on the dough handling properties of CDC Plentiful and Stettler wheat cultivars prepared at reduced (1.0% wt. by flour) and normal (2.0% wt. by flour) NaCl levels. Properties investigated include dough rheology, stickiness, and ratio of resistance to extension and extensibility. The inclusion of XYL and its combinations with GOX and HOX increased the stickiness, yielded lower dough strength indicated by rheology, and reduced the ratio of resistance to extension and extensibility. The inclusion of oxidative enzymes yielded a stronger dough, where HOX addition to dough had the lowest stickiness values and highest |G*| values, whereas GOX addition led to the highest ratio of resistance to extension—extensibility. NaCl only had minor effects overall on dough strength and stickiness for the cultivars studied. Overall, superior dough handling properties were observed with oxidative enzyme addition (GOX and HOX) suggesting that the increased crosslinking that occurs could aid in improving low sodium bread dough properties.     

A natural strategy to improve the shelf life of the loaf bread against toxigenic fungi: The employment of fermented whey powder

Whey powders are used as food ingredients in many applications, from bakery goods, soups and sauces to baby food. The objective of the study was to evaluate the antifungal property of a whey‐based medium (WM) fermented by lactic acid bacteria. The antifungal activity of the WM was evaluated using antifungal tests on solid and liquid media. MIC and MFC ranged from 15.6 to 250 mg/mL and 62.5 to 250 mg/mL, respectively. Using fermented WM for dough preparation produced a reduction of Penicillium expansum growth of 0.5–0.6 log CFU/g and an improvement in shelf life of 1–2 days in relation to control bread.     

Growth of Salmonella enterica Serovar Enteritidis PT4 in media containing glucose results in enhanced RpoS-independent heat and acid tolerance but does not affect the ability to survive air-drying on surfaces

The heat and acid tolerance of isolates of Salmonella enterica serovar Enteritidis PT4 was markedly higher if cells were grown to stationary phase in either commercially produced Tryptone Soya (TSBG) or brain–heart infusion (BHI) broth containing glucose than when cells were grown in either nutrient or Tryptone Soya broth without glucose. Differences between the populations were found to be related to the production of acid in either TSBG or BHI which caused the culture media pH values to fall to pH 5·8–4·7 during overnight incubation. This led to habituation, which increased both heat- and acid-tolerance, although there was no effect on the abilities of cells to survive air-drying on surfaces. The acid tolerance mechanisms, induced by fermentative growth in complex media, responsible for survival at pH 2·8, were RpoS-independent. In addition, although growth rates as measured by cfu were essentially the same in all media, optical density measurements were very different, with those of cells in media containing glucose being much higher. This was found to be due to the formation of larger cells by the Salmonella in these media.     

Antimicrobial Effects of Lactoferrin, Lysozyme, and the Lactoperoxidase System and Edible Whey Protein Films Incorporating the Lactoperoxidase System Against Salmonella enterica and Escherichia coli O157:H7

Lactoferrin (LF), lysozyme (LZ), the lactoperoxidase system (LPOS), and edible whey protein isolate (WPI) films incorporating LPOS were studied for inhibition of Salmonella enterica and Escherichia coli O157:H7. Antimicrobial effects of LF (5 to 40 mg/mL), LZ (1 to 20 mg/mL), and LPOS (0.5% to 5.0% [w/v] [0.03–.25 g/g, dry basis]) were examined by measuring turbidity of antimicrobial‐containing media after inoculation and by examining cell inhibition by WPI films incorporating LPOS (LPOS‐WPI films) on an agar recovery medium. Elastic modulus (EM), tensile strength (TS), percent elongation (%E), oxygen permeability (OP), and Hunter L, a and b of WPI films incorporating 0.03 to 0.25 g/g of LPOS were compared with those of plain WPI films without LPOS. The growth of S. enterica and E. coli O157:H7 (4 log colony‐forming units [CFU]/mL) in tryptic soy broth (TSB) was not prevented by LF at ≥20 and ≥40 mg/mL, respectively. S. enterica and E. coli O157:H7 in TSB were not inhibited by LZ at ≥ 6 and ≥ 20 mg/mL, respectively. LPOS at concentrations of 2.75% (w/v) and 1.0% (w/v) reduced S. enterica and E. coli O157:H7 to below the limit of detection (1 CFU/mL) in TSB, respectively. LPOS‐WPI films (0.15 g/g) completely inhibited S. enterica and E. coli O157:H7 (4 log CFU/cm²), inoculated either onto agar before placing the film disc or onto top of the film disc. Incorporation of 0.25 g/g of LPOS decreased EM, TS, and %E. The oxygen barrier property of WPI films was improved with the incorporation of LPOS at 0.15 to 0.25 g/g.     

Production of cyclopiazonic acid by aflatoxigenic and non-aflatoxigenic strains of Aspergillus flavus

96 strains of Aspergillus flavus isolated from samples of stored grain and smoke-dried meat products were examined for ability to produce cyclopiazonic acid and aflatoxins, grown on mycological broth medium and malt extract agar. Five strains produced cyclopiazonic acid in the range of 0.5 — 30 mg/kg and 9 produced aflatoxin B1 (0.1 — 14.8 mg/kg) but none of them produced both cyclopiazonic acid and aflatoxins.     

Antioxidant, antimicrobial, and anticancer activity of 3 Umbilicaria species

Abstract: The aim of this study is to investigate in vitro antioxidant, antimicrobial, and anticancer activity of the acetone extracts of the lichens Umbilicaria crustulosa, U. cylindrica, and U. polyphylla. Antioxidant activity was evaluated by 5 separate methods: free radical scavenging, superoxide anion radical scavenging, reducing power, determination of total phenolic compounds, and determination of total flavonoid content. Of the lichens tested, U. polyphylla had largest free radical scavenging activity (72.79% inhibition at a concentration of 1 mg/mL), which was similar as standard antioxidants in the same concentration. Moreover, the tested extracts had effective reducing power and superoxide anion radical scavenging. Total content of phenol and flavonoid in extracts was determined as pyrocatechol equivalent, and as rutin equivalent, respectively. The strong relationships between total phenolic and flavonoid contents and the antioxidant effect of tested extracts were observed. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method. The most active was extract of U. polyphylla with minimum inhibitory concentration values ranging from 1.56 to 12.5 mg/mL. Anticancer activity was tested against FemX (human melanoma) and LS174 (human colon carcinoma) cell lines using MTT method. All extracts were found to be strong anticancer activity toward both cell lines with IC₅₀ values ranging from 28.45 to 97.82 μg/mL. The present study shows that tested lichen extracts demonstrated a strong antioxidant, antimicrobial, and anticancer effects. That suggests that lichens may be used as possible natural antioxidant, antimicrobial, and anticancer agents.     

Impediometric detection of Campylobacter coli

The rapid automated bacterial impedance technique (RABIT) was examined as a method for the detection of two wild-type isolates of Campylobacter coli in broth media. Both isolates failed to produce a change in impedance that was sufficient for detection in any combination of six nonselective basal broth media, including Mueller-Hinton broth, nutrient broth no. 2, brain heart infusion broth supplemented with yeast extract (0.5% [wt/vol]), brucella broth, Campy broth supplemented with yeast extract (0.5% [wt/voll), and Whitley impedance broth, at 37 and 42 degrees C. Although the strains did proliferate in the media, changes in conductivity were very small (ranging from 0 to 1,000 microS) and were not significantly greater than the drift in conductance observed in the control broth medium. Additional work is therefore required to define a nonionic growth substrate that will produce charged ions upon metabolism that are detectable by RABIT.     

Sensitivity of Pseudomonas Strains to Polyphosphates in Media Systems

Of 13 gram positive and 12 gram negative microorganisms studied in nutrient broth (NB) containing 0.5% sodium salts of three polyphosphates, inhibition showed in seven strains of the former and only three of the latter. In an examination of sixteen Pseudomonas strains in NB, brain heart infusion (BHI) and trypticase soy broth (TSB) at 25°C and pH 7.0, tripoly- and hexametaphosphate were more effective inhibitors than pyrophosphate; the degree of inhibition was strain-dependent. Antibacterial activities were highest in the low-protein low-mineral media and were more pronounced when the compounds were filter-sterilized rather than heat-sterilized.     

Antibacterial Effects of Butylated Hydroxyanisole (BHA) against Bacillus species

The antibacterial effect of butylated hydroxyanisole (BHA) was evaluated in laboratory media and in two foods. In nutrient broth growth of Bucillus species (three strains of B. cereus, two of which were enterotoxigenic, and one strain each of B. subtilis and B. megaterium) was inhibited by 75 ppm of BHA. In tests with food systems growth inhibition of vegetative cells of these organisms required 1000 ppm in cooked rice and 5000 ppm in strained chicken. The effect of BHA was bacteriostatic at the tested levels (≤ 200 ppm in laboratory media and ≤ 10,000 ppm in the food systems), and viable cells were recovered from all samples. Bacterial growth resumed in samples which contained bacteriostatic levels of BHA after dilution with antioxidant free broth or food.     

Antimicrobial activity of Ginkgo biloba leaf extract on Listeria monocytogenes

ABSTRACT: The antimicrobial activities of Ginkgo biloba leaf extract (GBE) and the combined effects of GBE and sodium EDTA (sodium Ethylenediaminetetraacetic acid) against Listeria monocytogenes were determined at 4 °C, 25 °C, and 37 °C. Listeria monocytogenes grown at 37 °C for 24 h was inoculated (6 to 7 log CFU/mL) into BHI broth containing either GBE or GBE and EDTA (1.6 mg/mL) with various GBE concentrations of 0.1, 0.25, 0.5, 1, 2.5, 5.0, 7.5, 10.0, 15.0, or 20.0% vol/vol and stored at 4 °C, 25 °C, and 37 °C. The inhibitory effect of the GBE was more pronounced at low temperature of 4 °C. GBE was effective in inhibiting microbial growth. Addition of EDTA enhanced antimicrobial activity of GBE.     

Production of β-galactosidase for lactose hydrolysis in milk and dairy products using thermophilic lactic acid bacteria

The aim of this work was to establish optimal conditions for the maximum production of β-galactosidase using an industrially suitable medium. Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842 was cultivated in skim milk, whey and whey permeate basal media, supplemented with whey protein products, yeast extract or De Man–Rogosa–Sharpe (MRS) broth, at pH 5.6 and 43°C. All supplementations of the whey and whey permeate basal media resulted in the enhancement of the specific growth rates, rate of lactic acid production and β-galactosidase activity. However, unsupplemented skim milk gave the greatest rate of lactic acid production (3.50±0.269 mg lactic acid ml⁻¹ media h⁻¹) and the highest β-galactosidase activity (5.491±0.116 U activity ml⁻¹ media); far superior to the best whey-based medium supplemented with MRS (2.71±0.176 mg lactic acid ml⁻¹ media h⁻¹ and 3.091±0.089 U activity ml⁻¹ media, respectively). A technologically feasible approach for the reprocessing of the spent skim milk was tested and a conceptual process scheme is proposed.     

Antimicrobial Activities of Phenolic Extracts Derived from Seed Coats of Selected Soybean Varieties

Soybean hulls or seed coats consist of complex carbohydrates, proteins, lipids, and polyphenols such as anthocyanidins, proanthocyanidins, and isoflavones. The polyphenolics in the seed coats give them various colors such as black, brown, green, yellow, or even a mottled appearance. In this study, the antimicrobial effects of phenolic extracts from the seed coats of different colored soybeans (yellow, dark brown, brown, and black) were evaluated against foodborne pathogens such as Salmonella Typhimurium, Escherichia coli O157:H7, and Campylobacter jejuni in broth‐cultures as well as on chicken skin. The highest total phenolic content was observed for the phenolic extract from soybean variety (R07‐1927) with black colored seed coat (74.1 ± 2.1 mg chlorogenic acid equivalent [CAE]/g extract) and was significantly different (P <0.0001) from the extract of the conventional soybean variety (R08‐4004) with yellow colored seed coat (7.4 ± 1.2 mg CAE/g extract). The extract from black colored soybean produced reductions of 2.10 ± 0.08 to 2.20 ± 0.08‐log CFU/mL for both E. coli O157:H7 and C. jejuni after 3 d when incubated in broth‐culture having 4‐log CFU/mL of bacteria, whereas a 6 d incubation was found to reduce S. Typhimurium and E. coli O157:H7 at 2.03 ± 0.05 and 3.3 ± 0.08‐log CFU/mL, respectively. The extract also reduced S. Typhimurium and E. coli O157:H7 attached to chicken skin by 1.39 ± 0.03 and 1.24 ± 0.06‐log CFU/g, respectively, upon incubation for 6 d. Soybean seed coat extracts may have a potency as antimicrobial agents to reduce foodborne bacteria contaminating poultry products.     

Aqueous extraction kinetics of phenolic compounds from jamun (Syzygium cumini L.) seeds

In this study, aqueous extraction of phenolic compounds from jamun (Syzygium cumini L.) seed was undertaken. The effects of various parameters such as extraction temperature (34.8–85.2°C), extraction time (49.8–100.2 min), and liquid-to-solid ratio (9.8–60.2 mL/g) on the extraction yield, extract purity (i.e., total polyphenol content), and its antioxidant activities (1,1-diphenyl-2-picrlthydrazyl free radical scavenging assay and ferric reducing antioxidant power) were investigated. Response surface methodology was used to optimize the extraction conditions. The optimum extraction conditions (49.2°C, 89.4 min, and 51.6:1 mL/g) produced an extract with 17.3% extraction yield, high total polyphenol content (415 mg gallic acid equivalent/g dried extract) and significant antioxidant activity (IC₅₀: 35.4 ± 0.7 µg/mL). The high-performance liquid chromatography analysis of seed extract revealed the presence of gallic acid (90.8 mg/g dried extract), ellagic acid (36 mg/g dried extract), caffeic acid (26.07 mg/g dried extract), p-coumaric acid (0.26 mg/g dried extract), catechin (9.05 mg/g dried extract), epicatechin (0.42 mg/g dried extract), and quercetin (1.54 mg/g dried extract). Tannic acid (188.5 mg/g dried extract) was also identified as a major phenolic compound. The extraction kinetics was also studied and experimental data were fitted to four kinetic models such as first-order model, second-order model, Peleg’s model, and Minchev and Minkov model, to evaluate their applicability.