Whey Medium Research Articles

Effect of Lactococcus lactis UQ2 and its bacteriocin on Listeria monocytogenes biofilms

Listeria monocytogenes is a foodborne pathogen of major concern in food processing due to its wide environmental distribution and ability to form biofilms. Lactococcus lactis UQ2 is a bacteriocinogenic strain isolated from Mexican-style cheese, genetically identified as nisin A. It was grown on supplemented whey medium, representing an alternative, and probably more economical way to obtain this bacteriocin. A spray-dried crude bacteriocin fermentate (CBF) of L. lactis UQ2, or L. lactis UQ2 cells were used to test their antimicrobial activity against planktonic and sessile cells of L. monocytogenes Scott A on stainless steel chips. L. lactis UQ2 reduced >5 log cycles of this pathogen biofilms per chip, in competitive-exclusion tests at 37 °C. A new approach was developed to evaluate the antagonic effect of L. lactis UQ2 which outnumbered Listeria cells, by using fluorescent in situ hybridization utilizing labeled specific probes. An in vitro study showed that the combination of the two main antimicrobials produced by L. lactis UQ2 (lactic acid and nisin A) can be more efficient to suppress L. monocytogenes growth than each one on its own. This study may provide information to develop strategies to suppress or control L. monocytogenes biofilms on stainless steel surfaces, one of the most common materials used for food processing equipment.

Ethanol production from whey in bioreactor with co-immobilized enzyme and yeast cells followed by pervaporative recovery of product – Kinetic model predictions

A mathematical model for ethanol fermentation with yeast Saccharomyces cerevisiae and β-galactosidase on a whey medium was developed. Kinetic parameters of biomass growth were estimated using the least squares method on the basis of experimental data obtained in batch culture of suspended yeast cells growing on glucose and in batch fermentation with immobilized enzyme and yeast cells growing on lactose. Kinetic constants of separation of ethanol by pervaporation was estimated using experimental fluxes of permeate and separation coefficients of ethanol from broth. The degree of sugars utilization and the ethanol concentration in bioreactor as well as the time of ethanol separation needed to obtain the desired final concentration of recovered product can be predicted by using this model. The model can be also used for the investigation of influence of operating conditions on the fermentation yield and on the product concentration from broth. It can help as well in the optimization of process and in planning of experiments.

Applicability of pectate-entrapped Lactobacillus casei cells for l(+) lactic acid production from whey

Lactic acid is a versatile organic acid, which finds major application in the food, pharmaceuticals, and chemical industries. Microbial fermentation has the advantage that by choosing a strain of lactic acid bacteria producing only one of the isomers, an optically pure product can be obtained. The production of L: (+) lactic acid is of significant importance from nutritional viewpoint and finds greater use in food industry. In view of economic significance of immobilization technology over the free-cell system, immobilized preparation of Lactobacillus casei was employed in the present investigation to produce L: (+) lactic acid from whey medium. The process conditions for the immobilization of this bacterium using calcium pectate gel were optimized, and the developed cell system was found stable during whey fermentation to lactic acid. A high lactose conversion (94.37%) to lactic acid (32.95 g/l) was achieved with the developed immobilized system. The long-term viability of the pectate-entrapped bacterial cells was tested by reusing the immobilized bacterial biomass, and the entrapped bacterial cells showed no decrease in lactose conversion to lactic acid up to 16 batches, which proved its high stability and potential for commercial application.

Studies on a Neutral Exopolysaccharide of Lactobacillus fermentum TDS030603

A neutral exopolysaccharide produced in large amounts by Lactobacillus fermentum TDS030603 was purified from culture supernatants and its structure determined by monosaccharide analysis, methylation analysis and 1H-NMR spectroscopy. Optimum conditions for the production of this exopolysaccharide by the above bacterial strain, when cultured using cheese whey medium or MRS broth, were also investigated. The exopolysaccharide was found to be composed of D-galactose and D-glucose in the molar ratio of 1:2.5 and to consist of one major as well as one minor saccharide, both of which contained a tetrasaccharide repeating unit consisting of two α and two β anomers. The major saccharide contained non-reducing glucopyranose, O-3 substituted glucopyranose, O-6 substituted galactopyranose and O-2,3 disubstituted glucopyranose. The minor saccharide consisted of non-reducing galactopyranose, O-3 substituted glucopyranose, O-6 substituted galactopyranose and O-2,3 disubstituted glucopyranose. The results suggest that these exopolysaccharides are novel saccharides that differ from previously reported products of Lactobacillus fermentum strains. Their presence may contribute to the ropy properties of the medium.

Inhibitory effects of chromium(VI) and Remazol Black B on chromium(VI) and dyestuff removals by Trametes versicolor

Many dye-bearing wastewaters also contain heavy metal ions. Although the decolorization of single reactive dye or the uptake of single heavy metal ions by various growing cells has been extensively studied, very little attention has been given to the simultaneous bioremoval of reactive dye-metal ion systems. In this study, the single and combined effects of chromium(VI) and Remazol Black B reactive dye on the chromium(VI) and dye removal properties of adapted Trametes versicolor, a white-rot fungus, was investigated in a batch system at different levels of chromium(VI) and dye. Removal studies were performed at an initial pH of 4.0. Chromium(VI) uptake studies were carried out in two different growth media; mainly containing glucose and reduced quantity of glucose and whey. As the maximum microbial chromium(VI) uptake was accomplished in glucose + whey medium, single dye and binary dye-chromium(VI) bioremoval studies were also performed in this culture medium. Although the single removal of chromium(VI) and dye was enhanced with increasing initial concentration of each component up to 30 mg l −1 for chromium(VI) and up to 400 mg l −1 for dye, in general the presence of increasing concentrations of chromium(VI) ions much more severely inhibited the dye bioremoval by T. versicolor. While single chromium(VI) uptake efficiency was 32.2% in 30 mg l −1 chromium(VI) containing growth medium and single dye removal percent was 77.0% in 400 mg l −1 dye-bearing growth medium, the fungus was only capable of 10.8 and 13.3% removals of chromium(VI) and Remazol Black B dye, respectively, in the growth medium containing the binary mixture of these components at the above concentrations.

Beijerinckia indica L3 fermentation for the effective production of heteropolysaccharide-7 using the dairy byproduct whey as medium

A mutant strain of Beijerinckia indica L3 screened by a traditional chemical mutagenesis was grown in lactose-based mineral salts medium (MSM) for the production of heteropolysaccharide-7 (PS-7). The beta-galactosidase was expressed constitutively in the mutant and its activity was higher than that in parent strain. The highest amount of PS-7 produced by the mutant was 2.88 g/L with a viscosity of 4530 cP in lactose-based MSM medium. The PS-7 production was enhanced by the addition of 4 g/L glucose into lactose-based MSM medium, reaching 5.52 g/L with a viscosity of 39531 cP. PS-7 of 6.18 g/L with a viscosity of 45772 cP was produced from the mutant grown in whey medium. The PS-7 production from the mutant reached 7.04 g/L when 4 g/L glucose was added to the whey medium. Compositional analysis of PS-7 produced by the mutant grown in whey medium or lactose-based mineral salts medium showed that the ratios of glucose/rhamnose were maintained in the range similar to that of parent strain, indicating the same compositional structures of PS-7.

Production of gluconic acid from whey by free and immobilized Aspergillus niger

Deproteinized whey has been used as a fermentation medium for the production of gluconic acid by Aspergillus niger immobilized in polyurethane foam or free cells. Addition of a small amount of glucose (0.5%, w/v) in the whey medium enhanced the production of gluconic acid by 140% over the unsupplemented medium. Immobilized mycelia produced 92 g of gluconic acid from 1 L of whey medium containing 9.5% lactose and 0.5% glucose against 69 g by free mycelia. Immobilized mycelia can be reused.

Biochemical changes during fermentation of edible mushroom Pleurotus sajor-caju in whey

Some biochemical changes during growth of Pleurotus sajor-caju, an edible mushroom in deproteinized whey supplemented with diammonium hydrogen phosphate and indole-3-acetic acid were determined. Growth of P. sajor-caju in whey medium is a slow process. There was a time lag of 24 h for the onset of growth; however, logarithmic growth phase started after 120 h and maximum growth was obtained at 240 h. The protein content of mycelial material harvested at different growth phases was variable. The maximum protein could be harvested between 216 and 264 h of fermentation.

Production of exopolysaccharides by lactic acid bacteria isolated from traditional fermented foods in Nigeria

Lactic acid bacteria isolated from traditional fermented foods in Nigeria were investigated for their ability to produce exopolysaccharides (EPS). The test organisms were chosen after screening in a modified exopolysaccharide selection medium (mESM). The ability of the test organisms to produce EPS in whey medium (WM) and supplemented whey media (SWM I, SWM II) with combinations of lactose, KH2PO4, NH4Cl, casamino acids, mineral salts and yeast extract was determined. Amongst the test isolates, only Leuconostoc mesenteroides (from sorghum ogi) and Lactobacillus plantarum (from maize ogi) demonstrated the highest form of EPS production. Adjustment of the pH of SWM II to 6.2 increased the viscosity relative to that of SWM I (5.7) that was not adjusted. The effect of incubation temperature showed that at 25 °C, the viscosity was higher for L. mesenteroides and L. plantarum than at 30 and 40 °C. However, the biomass yield was lower, the least lactose was utilized and less lactic acid was produced at this temperature. More galactose and glucose were liberated at 30 °C that at 25 and 40 °C. This paper suggested that the viscous nature of some traditional foods in sub-Saharan Africa may be partly due to excretion of polysaccharides during the fermentation processes.

Lactobacillus helveticus growth and lactic acid production during pH-controlled batch cultures in whey permeate/yeast extract medium. Part II: kinetic modeling and model validation

A kinetic model was developed that describes growth and lactic acid production rates of Lactobacillus helveticus during pH-controlled batch cultures in whey permeate-yeast extract medium as a function of four variables: sugar, nitrogen substrate and lactic acid concentrations, and pH. Since available nitrogen substrate could not be measured directly, it was related to medium composition through a response surface model of maximum biomass concentration in nitrogen-limited growth cultures. The effect of pH on growth was modeled with a Gaussian equation instead of the traditional second order polynomial term. Product inhibition was modeled with a logistic term for lactate and an exponential term for undissociated lactic acid. The kinetic model accurately described the experimental data with few exceptions.

Isolation of a Kluyveromyces lactis Mutant Enriched in S-Adenosyl-L-Methionine and Growing in Whey Medium

The ability of six lactose-digesting yeast strains to accumulate S-adenosyl-L-methionine (AdoMet) when grown on whey medium was studied.Kluyveromyces lactis ATCC 8585 accumulated the greatest amount of AdoMet (15.2 mg per gram biomass) and was chosen for the development of an Ado-Met-enriched mutant. The Ado-Met-enriched mutant AM-65 was selected from mutants induced with N-methyl-N-nitro-N"-nitrosoguanidine. The strain accumulated 61.6 mg AdoMet per gram biomass. The effect of concentrations of medium components on AdoMet biosynthesis was studied. The ability of the mutant to accumulate AdoMet remained stable after multiple reinoculations.

Production of S-adenosyl- L-methionine by a mutant strain of Kluyveromyces lactis

S-Adenosyl-l-methionine (AdoMet) was produced by a mutant strain Kluyveromyces lactis AM-65 grown on whey. A full factorial design method of three factors – (NH4)2SO4 (factor x1), corn steep liquor (factor x2) and l-methionine (factor x3) on three levels – was used to determine the optimal medium conditions for the production of AdoMet. A time course shake-flask experiment in optimal whey medium (x1=3.1 g l−1, x2=12.7 g l−1, x3=4.6 g l−1) was also carried out and the results confirmed the results of the factorial design and subsequent quadratic modelling and optimization of AdoMet production which reached 90 mg g−1 cell dry wt.

Formulação de meios de cultivo à base de soro de leite para a produção de goma xantana por X. Campestris C7L

A goma xantana é um polissacarídeo microbiano de grande significado comercial especialmente para a indústria de alimentos. O objetivo deste trabalho foi avaliar a produção de xantana em diferentes meios de cultura à base de soro de leite utilizando o isolado Xanthomonas campestris C7L. Dentre as formulações testadas o meio de soro de leite integral produziu maior viscosidade e concentração final de xantana. Um sistema combinando soro integral (0,35% de proteína) e soro filtrado (0,18%de proteína) foi proposto. Na primeira fase em soro integral a produção de xantana foi de 13g/L e 45% de rendimento,enquanto que na segunda fase utilizando-se soro filtrado obteve-se um total de 28g/L de xantana e 75% de rendimento. O rendimento geral do processo foi de 55% e a viscosidade final do meio atingiu 18000cP. As soluções de xantana produzidas em soro de leite apresentaram comportamento pseudoplástico e tixotrópico característicos deste tipo de polímero. O isolado C7L demonstrou capacidade de produzir gomas de alta viscosidade e qualidade em soro de leite, constituindo uma alternativa promissora para a produção industrial de goma xantana a partir deste subproduto.

Construction of poly-met DNA yeast hybrids for increased methionine content: technofunctional properties of the hybrid yeasts.

Methionine is a limiting essential amino acid in human nutrition, to overcome the possible overdosage and improve bioavailability methionine supply should be in protein bound form. So insertion a poly-met encoding DNA sequence results a more efficient solution in increasing methionine content of yeast. Poly-met DNA yeast hybrids were constructed of Saccharomyces cerevisiae CB89, an auxotrophic mutant strain. Synthetic DNA sequence encoding methionine polypeptide was inserted into the polylinker region of pVT-U 100 vector with 2 mu plasmid replicon. After transformation of E. coli HB101 cells the efficiency of the ligation and transformation was checked by digesting the minipreps. S. cerevisiae CB89 was transformed with vector-poly-met insert and with the plasmid vector only as well. Hybrid yeasts were selected on uracilless medium. PVT-U 100 can be used as vector for the expression of DNA sequence in S. cerevisiae. The vector harbours the promoter of ADC1 gene immediately downstream from the promoter lies a polylinker sequence comprising unique restriction enzyme sites for BamHI, HindIII, PvuII, SacI, Xhol. The polylinker sequence is followed by the transcriptional stop site and polyadenylation signal of ADC1 gene. Plasmid pVT-U 100 has selection markers for S. cerevisiae (URA3) and for E. coli (amp, per F). Results show that the poly-met DNA hybrids methionine content is influenced by the length of the insert. Fusion hybrids containing 600 bp oligo insert showed the best values. Distribution of methionine content in the protein subfractions of polymet DNA hybrid and parent strain CB89 was determined in dependence of glucose concentration and aeration intensity. The increase in synthesized methionine appeared in fractions 1 + 2 and residue. Technofunctional properties of parent strains and hybrids were compared for whole cells and cell wall (residue). Results demonstrate that enrichment in methionine in the cell wall fraction resulted improvement of emulsifying ability. Bioavailability of methionine content was better in DNA hybrid yeast than in parent strain and was the best when propagated in whey medium.

Production of xanthan gum and ice-nucleating material from whey by Xanthomonas campestris pv. translucens

Xanthomonas campestris pv. translucens IFO13599 could produce xanthan gum (18.5 mg/100 mg, lactose) with lactose as the growth substrate in spite of a low level of β-galactosidase. This productivity corresponded to one-fifth that with glucose. This strain could also produce ice-nucleating material having an ice-nucleating temperature, T50, of −2.8 °C with xanthan gum in the culture broth. We found that this strain produced both materials in whey medium from which the insoluble components had been removed. The production of xanthan with ice-nucleating material reached a maximum after cultivation for 168 h under optimum conditions. Furthermore, the xanthan obtained had a low viscosity because of its variant structure revealed, by TLC and HPLC analyses, to be lacking pyruvic acid. Furthermore, we concluded that this mixture had considerable potential as a regeneratic agent, when compared to other regeneratic agents such as carboxymethylcellulose.

Production, partial purification and characterisation of lipases from Pseudomonas fragi CRDA 037

Pseudomonas fragi CRDA 037 produced extracellular (exo-) and intracellular (endo-) lipases when grown in whey media. Partially purified lipase extracts were obtained by precipitation with solid ammonium sulphate at 20–40% saturation for the exolipase and 20–60% saturation for the endolipase. Native polyacrylamide gel electrophoresis of the exolipase showed the presence of a major band with a molecular weight ( M r ) of 25·5 kDa, whereas the endolipase showed the presence of three fractions with M r of 35·5, 49 and 70 kDa. The pH optima for the exo- and endolipases were 8·75 and 9·0, respectively. Substrate specificity determinations were performed with triacetin, tributyrin, trimyristin and triolein, where exo- and endolipase demonstrated higher affinity for trimyristin, with K m values of 5·11 and 3·24 m m, respectively. Inhibition of the exo- and endolipase occurred in the presence of a range of chemicals, including sodium deoxychelate, ferrous and ferric chloride, diisopropyl fluorophosphate, N-bromosuccinimide and 5,5-dithiobis-(-2-nitrobenzoic acid).

A novel recycle batch immobilized cell bioreactor for propionate production from whey lactose

Recycle batch fermentations using immobilized cells of Propionibacterium acidipropionici were studied for propionate production from whey permeate, de-lactose whey permeate, and acid whey. Cells were immobilized in a spirally wound fibrous sheet packed in a 0.5-L column reactor, which was connected to a 5-L stirred tank batch fermentor with recirculation. The immobilized cells bioreactor served as a breeder for these recycle batch fermentations. High fermentation rates and conversions were obtained with these whey media without nutrient supplementation. It took approximately 55 h to ferment whey permeate containing approximately 45 g/L lactose to approximately 20 g/L propionic acid. Higher propionate concentrations can be produced with various concentrated whey media containing more lactose. The highest propionic acid concentration obtained with the recycle batch reactor was 65 g/L, which is much higher than the normal maximum concentration of 35 to 45 g/L reported in the literature. The volumetric productivity ranged from 0.22 g/L x h to 0.47 g/L x h, depending on the propionate concentration and whey medium used. The corresponding specific cell productivity was 0.033 to 0.07 g/L x g cell. The productivity increased to 0.68 g/L x h when whey permeate was supplemented with 1% (w/v) yeast extract. Compared with conventional batch fermentation, the recycle batch fermentation with the immobilized cell bioreactor allows faster fermentation, produces a higher concentration of product, and can be run continually without significant downtime. The process also produced similar fermentation results with nonsterile whey media.

Proline-Specific Peptidases of Lactobacillus casei Subspecies

This paper describes the specific activities for proline iminopeptidases, x-prolyl dipeptidyl peptidase and post proline endopeptidase, from each of two subspecies of Lactobacillus casei grown in MRS broth and whey media at 37°C, pH 6.0. The histochemical PAGE of soluble extracts from one subspecies (Lactobacillus casei ssp. casei LLG) indicated that the two enzyme activities were due to distinct proteins. Except for a slight increase in x-prolyl dipeptidyl peptidase activity, the activities of proline imino- and endopeptidases of cells grown in whey medium did not vary markedly from those of cells grown in MRS broth. The effect of inhibitor agents and pH on the activities of proline iminopeptidase and x-prolyl dipeptidyl peptidase were investigated. The temperature optima and storage stability under different conditions were also studied for these activities.

Whey as a growth medium for two spp. of Azospirillum grown in batch culture

Summary The growth curves of Azospirillum lipoferum 4B and Azospirillum brasilense NO 40 grown on raw whey, deproteinized whey and malate media were investigated in batch culture. A maximal cell density of 14 × 108 and 4.5 × 10 8 cell/ml were attained after 72 h of the growth of Azospirillum brasilense NO40 and Azospirillum lipoferum 4B on deproteinized whey medium respectively. Raw whey as well as deproteinized whey was successfully utilized by both strains in a similar manner to that of malate. The highest growth of A. lipoferum 4B and A. brasilense NO40 was detected when 20 ml/l of raw whey or deproteinized whey were used as a carbon source in the basal medium. Prospective economic balance for the capital cost of malate and whey or deproteinized whey growth media was also discussed.

Yoghurt whey medium for food‐borne yeasts

SummaryA selective medium based on yoghurt whey was developed for the enumeration of yeasts in foods. Yoghurt whey agar (YWA) was prepared by mixing one part of a sterile agar solution (5%) with two parts of a sterile whey filtrate obtained from autoclaved (121°C, 20min) plain set yoghurt. the performance of YWA in the enumeration of yeasts was compared with that of plate count agar plus antibiotics (APCA) and acidified potato dextrose agar (PDA‐A) by examining food samples and broth cultures of known yeast isolates. APCA ranked first, confirming the superiority of antibiotic amended media over the acidified ones. the overall performance of YWA was comparable to that of PDA‐A.