Mycoflora study in a wheat flour mill of Argentina

The mycoflora of the environment: wheat conditioning, milling and screening, and filling zone, as well as, raw material -wheat-, intermediate product -grits- and end product -flour- on day 1, and after cleaning improvements -days 45 and 90- were studied in an Argentine wheat mill. Samples were incubated at 28°C for 5-7 days on Malt Extract Agar with chloramphenicol (100 mg L-1) and the results were expressed in colony forming units per cubic meter of air (CFU m-3) or per gram of sample (CFU g-1), respectively. Fungal genera and species were isolated and identified and the potential toxicogenic capacity of the Aspergillus flavus and Fusarium graminearum isolated was studied. Time-Place and Time-Product multifactorial ANOVA were carried out. After cleaning improvements, CFU m-3 of air decreased as a function of time. Cladosporium and Alternaria were abundant in every zone, Aspergillus predominated in the wheat conditioning zone and Penicillium and Eurotium decreased with time. Wheat was more contaminated than grits and flour; Aspergillus, Eurotium and Mucoraceae family were the most abundant. Deoxynivalenol was above the levels allowed in wheat, being acceptable in grits and flour. Aflatoxin and Zearalenone showed acceptable levels. When studied in vitro, 53% of Aspergillus flavus and 100% of Fusarium graminearum isolates, produced Total Aflatoxins, and Deoxynivalenol and Zearalenone, respectively.

Exposure assessment of mycotoxins in cow's milk in Argentina.

A stochastic simulation model was developed to carry out the first quantitative risk exposure assessment of the mycotoxin level in cow's milk produced in Argentina. The prevalence and concentration of aflatoxin M1 (AFM1), deoxynivalenol (DON) and zearalenone (ZEA) were modeled at various stages through milk processes complying with Argentinean practices. Concentration of AFM1 (0.059ppb), DON (0.338ppb) and ZEA (0.125ppb) in dairy milk were estimated. The proportion of feed samples that exceeded the maximum level accepted by European regulations for AFB1, DON and ZEA were estimated at 25.07%, 0.0% and 8.9%, respectively. The percentage of milk samples that exceeded the maximum level accepted for AFB1 by the MERCOSUR (0.5ppb) and the European Union regulations (0.05ppb) were 0.81 and 32.65, respectively. The probability distribution of AFM1 concentration in milk was affected by the carry-over rate equations applied in the model. Mycotoxin levels in corn silage and concentrated feeds were the factors most correlated with mycotoxin concentrations in milk. Therefore, agricultural practices, crop management and feed production require prompt attention regarding mycotoxin issues.

Mycoflora study in a wheat flour mill of Argentina.

THE MYCOFLORA OF THE ENVIRONMENT: wheat conditioning, milling and screening, and filling zone, as well as, raw material -wheat-, intermediate product -grits- and end product -flour- on day 1, and after cleaning improvements -days 45 and 90- were studied in an Argentine wheat mill. Samples were incubated at 28°C for 5-7 days on Malt Extract Agar with chloramphenicol (100 mg L(-1)) and the results were expressed in colony forming units per cubic meter of air (CFU m(-3)) or per gram of sample (CFU g(-1)), respectively. Fungal genera and species were isolated and identified and the potential toxicogenic capacity of the Aspergillus flavus and Fusarium graminearum isolated was studied. Time-Place and Time-Product multifactorial ANOVA were carried out. After cleaning improvements, CFU m(-3) of air decreased as a function of time. Cladosporium and Alternaria were abundant in every zone, Aspergillus predominated in the wheat conditioning zone and Penicillium and Eurotium decreased with time. Wheat was more contaminated than grits and flour; Aspergillus, Eurotium and Mucoraceae family were the most abundant. Deoxynivalenol was above the levels allowed in wheat, being acceptable in grits and flour. Aflatoxin and Zearalenone showed acceptable levels. When studied in vitro, 53% of Aspergillus flavus and 100% of Fusarium graminearum isolates, produced Total Aflatoxins, and Deoxynivalenol and Zearalenone, respectively.

Robust experimental design for optimizing the microbial inhibitor test for penicillin detection in milk.

AIMS: To use experimental design techniques and a multiple logistic regression model to optimize a microbiological inhibition test with dichotomous response for the detection of Penicillin G in milk. METHODS AND RESULTS: A 2(3) x 2(2) robust experimental design with two replications was used. The effects of three control factors (V: culture medium volume, S: spore concentration of Geobacillus stearothermophilus, I: indicator concentration), two noise factors (Dt: diffusion time, Ip: incubation period) and their interactions were studied. The V, S, Dt, Ip factors and V x S, V x Ip, S x Ip interactions showed significant effects. CONCLUSIONS: The use of 100 microl culture medium volume, 2 x 10(5) spores ml(-1), 60 min diffusion time and 3 h incubation period is recommended. In these elaboration conditions, the penicillin detection limit was of 3.9 microg l(-1), similar to the maximum residue limit (MRL). Of the two noise factors studied, the incubation period can be controlled by means of the culture medium volume and spore concentration. SIGNIFICANCE AND IMPACT OF THE STUDY: We were able to optimize bioassays of dichotomous response using an experimental design and logistic regression model for the detection of residues at the level of MRL, aiding in the avoidance of health problems in the consumer.

Natural occurrence of nivalenol and mycotoxigenic potential of Fusarium graminearum strains in wheat affected by head blight in Argentina

The principal agents of Fusarium head blight in the main cropping area of Argentina were investigated in heavily infected samples. The ability of the isolates to produce trichothecenes was determined by GC and HPLC. Fusarium graminearum was the predominant species and of 33 isolates, 10 produced deoxinivalenol (DON) (0.1- 29 mg kg-1), 13 produced both deoxinivalenol (1.0- 708 mg kg-1) and nivalenol (0.1- 6.2mg kg-1), 12 produced 3-acetyldeoxinivalenol (0.1- 14 mg kg-1), 13 produced 15-acetyldeoxinivalenol (0.1- 1.9 mg kg-1), 10 produced Fusarenone X (0.1- 2.4 mg kg-1) and 7 produced zearalenone (0.1- 0.6 mg kg-1). These results suggest that F. graminearum strains isolated from the wheat growing regions in Argentina belong to DON chemotype. Although some strains produced both deoxinivalenol and nivalenol, nivalenol was produced in lower levels. The natural occurrence of nivalenol in wheat affected by head-blight collected in the main production area during two years (2001-2002) was also determined. From 19 samples 13 were contaminated with deoxinivalenol in a range of 0.3 to 70 mg kg-1and 2 samples with both deoxinivalenol (7.5 and 6.7 mg kg-1) and nivalenol (0.05 and 0.1 mg kg-1), respectively. This is the first report of natural occurrence of nivalenol in wheat cultivate in Argentina.

O principal causador de giberela no trigo na Argentina e sua capacidade de produzir tricotecenos foram estudados por GC e HPLC em amostras altamente infectadas. A espécie predominante foi Fusarium graminearum, sendo que de um total de 33 isolados, 10 produziram deoxinivalenol (0,1-29 mg kg -1), 13 produziram deoxinivalenol (1,0-708 mg kg-1) e nivalenol (0,1-6,2 mg kg-1), 12 produziram 3-acetildeoxinivalenol (0,1-14 mg kg-1), 13 produziram 15-acetildeoxinivalenol (0,1-1,9 mg kg-1), 10 produziram fusarenona X (0,1- 2,4 mg kg-1) e 7 produziram zearalenona (0,1- 0,6 mg kg-1). Esses resultados sugerem que as cepas de F. graminearum isoladas de trigo cultivado na Argentina pertencem ao quimiotipo DON. Embora algumas cepas tenham produzido tanto DON quanto NIV, NIV foi produzido em quantidade inferior ao DON. A ocorrência natural de nivalenol em trigo afetado pela giberela coletado na principal área de produção durante dois anos (2001-2002) foi também determinada. De 19 amostras, 13 estavam contaminadas com deoxinivalenol na faixa de 0,3 a 70 mg kg-1 e 2amostras continham tanto deoxinivalenol (7,5 e 6,7 mg kg-1) quanto nivalenol (0,05 e 0,1 mg kg-1), respectivamente. Esse é o primeiro relato da ocorrência de nivalenol em trigo cultivado na Argentina.

Natural occurrence of nivalenol and mycotoxigenic potential of Fusarium graminearum strains in wheat affected by head blight in Argentina.

The principal agents of Fusarium head blight in the main cropping area of Argentina were investigated in heavily infected samples. The ability of the isolates to produce trichothecenes was determined by GC and HPLC. Fusarium graminearum was the predominant species and of 33 isolates, 10 produced deoxinivalenol (DON) (0.1- 29 mg kg(-1)), 13 produced both deoxinivalenol (1.0- 708 mg kg(-1)) and nivalenol (0.1- 6.2mg kg(-1)), 12 produced 3-acetyldeoxinivalenol (0.1- 14 mg kg(-1)), 13 produced 15-acetyldeoxinivalenol (0.1- 1.9 mg kg(-1)), 10 produced Fusarenone X (0.1- 2.4 mg kg(-1)) and 7 produced zearalenone (0.1- 0.6 mg kg(-1)). These results suggest that F. graminearum strains isolated from the wheat growing regions in Argentina belong to DON chemotype. Although some strains produced both deoxinivalenol and nivalenol, nivalenol was produced in lower levels. The natural occurrence of nivalenol in wheat affected by head-blight collected in the main production area during two years (2001-2002) was also determined. From 19 samples 13 were contaminated with deoxinivalenol in a range of 0.3 to 70 mg kg(-1)and 2 samples with both deoxinivalenol (7.5 and 6.7 mg kg(-1)) and nivalenol (0.05 and 0.1 mg kg(-1)), respectively. This is the first report of natural occurrence of nivalenol in wheat cultivate in Argentina.

Mycotoxins inactivation by extrusion cooking of corn flour.

AIMS: To evaluate the effects of the extrusion cooking process on the inactivation of mycotoxins in corn flour. METHODS AND RESULTS: Samples of corn flour experimentally contaminated with aflatoxin B1 (AFB1) (50 ppb) and deoxynivalenol (DON) (5 ppm) were extruded. The effects of three extrusion variables (flour moisture, extrusion temperature and sodium metabisulphite addition) were analysed according to a two-level factorial design. The process was effective for the reduction of DON content (higher than 95%) under all the conditions assessed, but was only partially successful (10-25%) for the decontamination of AFB1. CONCLUSION: Extrusion cooking is effective for the inactivation of DON but is of limited value for AFB1, even if metabisulphite is added. More severe extrusion conditions are needed for the detoxification of AFB1. SIGNIFICANCE AND IMPACT OF THE STUDY: As contamination with DON occurs mainly in the field prior to harvesting and that of AFB1 is normally produced during grain storage, maize is often contaminated with DON but not with AFB1. Under these conditions, the described extrusion process can be used for the detoxification of DON. The addition of sodium metabisulphite did not significantly affect the inactivation of AFB1. Extrusion cooking is therefore an appropriate treatment for vomitoxin-contaminated maize in countries where, because of the prevailing conditions, these are the only toxins present.

Characterization and control of thread mould in cheese.

AIMS: The origin of a mould responsible for the contamination of an Argentinian cheese factory was identified and several antifungal treatments were assessed. METHODS AND RESULTS: Moulds were isolated and identified from vacuum-packed hard cheeses, from the environment and from the surfaces of the factory. A suspension conidia test containing different fungicides was performed; another assay involved the fumigation with p-OH fenilsalicidamide. Only Phoma glomerata was found in all of the mouldy cheeses, and was also obtained from different environments and machine surfaces. The most effective treatments against P. glomerata isolates were 0.5% (w/v) natamycin and 2% (v/v) parabens. Fumigation with p-OH fenilsalicidamide showed no satisfactory results. CONCLUSION: P. glomerata is an important thread mould-contaminating agent in vacuum-packed hard cheeses. SIGNIFICANCE AND IMPACT OF THE STUDY: Taking into account the survival of the conidia of the P. glomerata isolates to different antifungal treatments, the sources of contamination need to be controlled by designing a good factory layout.

Mycotoxins and toxigenic fungi.

Mycotoxins and the fungi that produce them are of increasing importance as causes of human illness, but the diseases produced remain poorly understood at the clinical level. This paper explores four aspects: the increase of interest in ochratoxin A, factors affecting mycotoxin production, toxicology of the major mycotoxins, and the identification of Penicillium species which cause food spoilage and are important in indoor air.

Inhibitory effects of some spice essential oils on Aspergillus ochraceus NRRL 3174 growth and ochratoxin A production.

Inhibitory effects of essential oils of oregano (Origanum vulgare), mint (Menta arvensis), basil (Ocimum basilicum), sage (Salvia officinalis) and coriander (Coriandrum sativum), on the mycelial growth and ochratoxin A production by Aspergillus ochraceus NRRL 3174 were studied. Cultures were incubated on yeast extract-sucrose (YES) broth, at concentrations of 0, 500, 750 and 1000 p.p.m. of essential oils during 7, 14 and 21 d at 25 degrees C. At 1000 p.p.m., oregano and mint completely inhibited the fungal growth and ochratoxin A production up to 21 d, while basil was only effective up to 7 d. At 750 p.p.m., oregano was completely effective up to 14 d, whereas mint allowed fungal growth but no ocratoxin A production up to 14 d. At 500 p.p.m., no evident inhibition could be in observed with any of the essential oils under analysis. Sage and coriander showed no important effect at any of the concentrations studied. These inhibitory effects are interesting in connection with the prevention of mycotoxin contamination in many foods and they could be used instead of synthetic antifungal products.

Estudio de la flora fúngica ambiental de la biblioteca de la Facultad de Ingeniería Química. Universidad Nacional del Litoral / Study the environmental fungi at the library of the Faculty of Chemical Engineering (UNL)

Se analizó la flora fúngica ambiental de la biblioteca de la Facultad de Ingeniería Química de la Universidad Nacional del Litoral, Santa Fe, a los fines de evaluar los posibles riesgos tantos para la salud de los asistentes como por el probable deterioro de las colecciones existentes. El muestreo se realizó con un equipo SAS (sistema de aire sólido) que aspira 100 litros de aire por minuto, a 1,5 m de altura durante un min., por duplicado, entre las 11,30 y 12,30 horas. Se utilizó MEA + antibiótico (agar extracto de malta, cloranfenicol 100 mg por ciento). Se llevaron a cabo dos muestreos en condiciones ambientales diferentes: Muestreo A: Temperatura 16,5 ºC, Humedad Relativa 75 por ciento, Presión 1015,4 hPa. El salón de publicaciones periódicas presentó una carga fúngica de 25 UFC/m3 y el archivo 95 UFC/m3. Los géneros fúngicos aislados fueron: Cladosporium spp, Penicillium sp, Trichoderma sp, Aspergillus spp, Alternaria sp y Acremonium sp. Muestreo B: Temperatura 20 ºC, Humedad Relativa 95 por ciento, Presión 1013,7 hPa. El salón de publicaciones periódicas presentó una carga fúngica de 290 UFC/m3 y el archivo 360 UFC/m3. Los géros fúngicos aislados fueron: Cladosporium spp, Humicola sp, Aspergillus spp, Alternaria sp y Acremonium sp. Si bien en ambos muestreos no se detectaron valores altos de contaminación, éstos resultaron significativamente superiores en condiciones de humedad relativa y temperatura mayores. Se destaca que alguno de los mohos aislados como: Trichoderma viride y Humicola sp poseen una lata capacidad celulolítica deteriorante y otros: Cladosporium spp, Aspergillus spp, Acremonium sp y Alternaria sp son agentes de reconocida participación en procesos clínicos patógenos y en afecciones alérgicas

Estudio de la flora fúngica ambiental de la biblioteca de la Facultad de Ingeniería Química. Universidad Nacional del Litoral / Study the environmental fungi at the library of the Faculty of Chemical Engineering (UNL)

Se analizó la flora fúngica ambiental de la biblioteca de la Facultad de Ingeniería Química de la Universidad Nacional del Litoral, Santa Fe, a los fines de evaluar los posibles riesgos tantos para la salud de los asistentes como por el probable deterioro de las colecciones existentes. El muestreo se realizó con un equipo SAS (sistema de aire sólido) que aspira 100 litros de aire por minuto, a 1,5 m de altura durante un min., por duplicado, entre las 11,30 y 12,30 horas. Se utilizó MEA + antibiótico (agar extracto de malta, cloranfenicol 100 mg por ciento). Se llevaron a cabo dos muestreos en condiciones ambientales diferentes: Muestreo A: Temperatura 16,5 ºC, Humedad Relativa 75 por ciento, Presión 1015,4 hPa. El salón de publicaciones periódicas presentó una carga fúngica de 25 UFC/m3 y el archivo 95 UFC/m3. Los géneros fúngicos aislados fueron: Cladosporium spp, Penicillium sp, Trichoderma sp, Aspergillus

[Incidence of Fusarium toxins in corn and milling byproducts]. / Incidencia de toxinas de Fusarium en el maíz y productos de la molienda.

The incidence of Fusarium toxins-trichothecenes and zearalenone in 100 samples of whole grains as well as their distribution in the by-products (arising of 32 whole corn samples) of the wet-grinding of corn were studied, the samples coming from the central and northern areas of the Santa Fe Province, Argentina. The analyses were carried out by thin-layer chromatography. A 33% of the samples was found to be contaminated by deoxynivalenol (DON), its amount ranging from traces to 1,200 micrograms/Kg; 15% of the samples contained T-2 toxin from 900 to 2,400 micrograms/Kg and only traces of zearalenone were detected in one sample. Only few samples (7%) included diacetoxiscirpenol (DAS), nivaleno (NIV) and neosolaniol (NS) and 7% of the samples evidenced contamination by more than one mycotoxin. It is worth noticing that DON was found to be contaminating only those by-products destined to human consumption. Conversely, T-2 toxin was found in by-products destined to both human and animal consumption.

[Biological value of the unicellular protein of Kluyveromyces marxianus var. lactis]. / Estudio del valor biológico de la proteína unicelular de. Kluyveromyces marxianus var. lactis.

The ever increasing problem of environmental pollution and protein scarcity led us to begin producing protein biomass from cheese whey, having selected for this aim, Kluyveromyces marxianus va. lactis strain, which represents the right relationship between its protein content (53.3% d.w.) and that of the RNA (4.63% d.w.). On the other hand, the distribution of its essential amino acids is balanced, although it shows a deficiency in methionine, its value being 1.5 g/16 gN. The purpose of this work was to assess the biological quality of this protein concentrate, so as to use it in animal feeding. Protein quality was determined by the NPU method (net protein utilization), according to Miller and Bender's technique. Three balanced diets were prepared (10% protein), the test sample with casein, and the rest with protein biomass, one of then supplemented with methionine (0.5 g/100 g food). Based on the results it can be concluded that the biomass analyzed has an adequate biological value (55.37%) for use in animal feeding, especially when methionine as added (60.23%).

[Production of non-volatile amines by strains of enterococci]. / Producción de aminas no volátiles por cepas de enterococos.

During the last few years there has been great interest concerning the problems related with the presence of pressor amines in different kinds of cheese, specially since the "cheese syndrome" was made evident. Since the capacity of the bacterial groups involved in cheese manufacture to produce these amines has not yet been clarified, it was decided to study the production capacity of tyramine, tryptamine and histamine of enterococci strains probably used in the starter cultures. Forty-one enterococci strains were analysed cultivating them in milk and in milk with the addition of the corresponding aminoacids. It was determined that only low percentages of Streptococcus faecalis subsp. liquefaciens and Streptococcus durans strains (34% and 11% respectively) produced traces of tyramine and tryptamine in milk. But when cultivated in the presence of the corresponding aminoacids, a large percentage of strains of all the species produced tyramine in high concentrations and different percentages of them produced tryptamine in concentrations no higher than 200 ppm. All strains analysed proved to be unable to produce histamine. It can be concluded that there exists a strong probability for enterococci to produce tyramine and tryptamine in different concentrations specially when developed in the presence of the corresponding aminoacids.

Producción de aminas no volátiles por cepas de enterococos. / [Production of non-volatile amines by strains of enterococci]

During the last few years there has been great interest concerning the problems related with the presence of pressor amines in different kinds of cheese, specially since the [quot ]cheese syndrome[quot ] was made evident. Since the capacity of the bacterial groups involved in cheese manufacture to produce these amines has not yet been clarified, it was decided to study the production capacity of tyramine, tryptamine and histamine of enterococci strains probably used in the starter cultures. Forty-one enterococci strains were analysed cultivating them in milk and in milk with the addition of the corresponding aminoacids. It was determined that only low percentages of Streptococcus faecalis subsp. liquefaciens and Streptococcus durans strains (34

and 11

respectively) produced traces of tyramine and tryptamine in milk. But when cultivated in the presence of the corresponding aminoacids, a large percentage of strains of all the species produced tyramine in high concentrations and different percentages of them produced tryptamine in concentrations no higher than 200 ppm. All strains analysed proved to be unable to produce histamine. It can be concluded that there exists a strong probability for enterococci to produce tyramine and tryptamine in different concentrations specially when developed in the presence of the corresponding aminoacids.

[Incidence of Bacillus cereus in powdered dehydrated food]. / Incidencia de Bacillus cereus en alimentos deshidratados en polvo.

Bacillus cereus incidence on dehydrated powdered foods on sale in supermarkets of Santa Fe city was studied. Two hundred and fifty samples of five different foods: desserts, soups, mousses, pre-cooked "polenta" and mashed potatoes, were examined. Toxinogenic activity of strains confirmed as B. cereus by means of the test of lethality in rats, was analyzed. The ratio between contaminated samples and total analyzed samples was always greater than 6% (Table 1). Besides, none of the analyzed foods exceeded acceptability maximum limit (10(5) UFC/g), established by I.C.M.S.F. (Table 2). It was checked in all cases that no simple lineal correlation existed between B. cereus and total aerobic bacteria enumerations. On the other hand, the percentage of strains with lethal effects was in all cases greater than 42.8% (Table 3).

Toxicidad de cepas de Fusarium aisladas de alimentos / Toxicity of Fusarium strain isolated of foods

Se estudió la capacidad toxicoténica de cepas de Fusarium contaminantes de productos vegetales destinados a la alimentación humana y animal. Se empleó una prueba basada en la acción fitotóxica que manifiestan los tricotecenos sobre semillas de Lepidium sativum. Se analizaron 110 muestras (cereales y subproductos y papa) de las cuales se aislaron e identificaron 24 cepas de F. moniliforme, 2 de F. semitectum y 7 de F. solani, cuya capacidad toxicogénica se estudió cultivándolas em medio PSA y en medios naturales. El 9% del total de las cepas aisladas resultó tóxico en el medio PSA. Cuando se estudiaron en los medios naturales correspondientes, se verificó tanto en las provenientes de sorgo como de maíz, un aumento en el porcentaje de cepas toxicogénicas y también un aumento en el grado de toxicidad. Las cepas provenientes de papa no presentaron toxicidad en ninguno de los dos medios. Puede observarse que existe una estrecha relación entre el medio de cultivo en el cual se desarrollan la s cepas y su grado de toxicidad. En base a ésto, se aconseja que el estudio se realice con el empleo de medios de cultivo naturales. Por otra parte, debido a la simplicidad, bajo costo y alta sensibilidad de la prueba se considera que la misma puede aplicarse para extender el estudio a cepas de Fusarium contaminantes de otros productos alimenticios, con el objeto de conocer el riesgo real que implican los tricotecenos para la salud

Toxicidad de cepas de Fusarium aisladas de alimentos / Toxicity of Fusarium strain isolated of foods

Se estudió la capacidad toxicoténica de cepas de Fusarium contaminantes de productos vegetales destinados a la alimentación humana y animal. Se empleó una prueba basada en la acción fitotóxica que manifiestan los tricotecenos sobre semillas de Lepidium sativum. Se analizaron 110 muestras (cereales y subproductos y papa) de las cuales se aislaron e identificaron 24 cepas de F. moniliforme, 2 de F. semitectum y 7 de F. solani, cuya capacidad toxicogénica se estudió cultivándolas em medio PSA y en medios naturales. El 9% del total de las cepas aisladas resultó tóxico en el medio PSA. Cuando se estudiaron en los medios naturales correspondientes, se verificó tanto en las provenientes de sorgo como de maíz, un aumento en el porcentaje de cepas toxicogénicas y también un aumento en el grado de toxicidad. Las cepas provenientes de papa no presentaron toxicidad en ninguno de los dos medios. Puede observarse que existe una estrecha relación entre el medio de cultivo en el cual se desarrollan la s cepas y su grado de toxicidad. En base a ésto, se aconseja que el estudio se realice con el empleo de medios de cultivo naturales. Por otra parte, debido a la simplicidad, bajo costo y alta sensibilidad de la prueba se considera que la misma puede aplicarse para extender el estudio a cepas de Fusarium contaminantes de otros productos alimenticios, con el objeto de conocer el riesgo real que implican los tricotecenos para la salud (AU)

[Optimizing conditions for the discontinuous production of unicellular protein using whey]. / Optimización de condiciones para la producción discontínua de proteína unicelular utilizando suero de leche.

The cheese whey is one of the most important effluents which is being disposed off in our area. That is why the study for optimizing conditions in the process of recovering whey to produce protein biomass in a batch fermenter was undertaken. A yeast strain (Kluyveromyces marxianus var. lactis) was propagated on a medium based on whey from cheese making plants, the following conditions for cell development being optimized: temperature, pH and initial concentration of lactose. A methodology based on performing several tests ordered according to a "Latin Squares" structure was proposed; this enables the simultaneous study of three variables with a small number of experiences. Such experiences were performed in a cylindrical (air lift type) glass fermenter, obtaining a maximum yield (4.78 g/l by dry weight) when working with an initial lactose concentration equal to 4.8%. For all temperatures (27, 30 and 35 degrees C) and pH (3, 4 and 5) employed, an increase in the cell number occurred with the initial lactose concentration increasing from 2% to 4.8% (Table 2). It is preferable to work at 27 degrees C and pH 4 (since these conditions minimize the bacterial contamination) and with a lactose concentration equal to 4.8%, i.e. the concentration in the residual cheese whey. Thus, an optimum yield in protein biomass is obtained, enabling a good utilization of this effluent, and also diminishing its initial BOD from 60,000 to 15,000 ppm.