Resumo − O objetivo deste trabalho foi avaliar os efeitos da temperatura, pH, relação enzima:substrato (E:S) e tempo de reação sobre a hidrólise enzimática da caseína do leite de cabra Moxotó, com uso de diferentes enzimas proteolíticas. A hidrólise enzimática da caseína caprina foi realizada com uso de tripsina, pepsina e papaína. Para cada enzima, foram utilizados dois níveis de cada variável, na avaliação de seus efeitos sobre a hidrólise da caseína, em um fatorial completo 2 4 . Os produtos da hidrólise foram visualizados em eletroforese SDS-PAGE. O melhor valor do grau de hidrólise com a enzima papaína foi obtido em pH 6,5, E:S de 1:150 e 5 horas de hidrólise a 50ºC (28,17%); com a tripsina, em pH 8,5, E:S de 1:150 e 5 horas a 40ºC (29,55%); e com a pepsina, em pH 3,0, E:S de 1:100 e 5 horas a 40ºC (38,27%). A hidrólise da caseína caprina é influenciada positivamente pelo pH e tempo de hidrólise, com o uso da pepsina. Foram observadas interações significativas antagônicas entre pH e relação E:S, com o uso da tripsina; e entre pH, temperatura e tempo de hidrólise, com o uso da papaína. A pepsina apresenta elevada eficiência na hidrólise de α s1 , β e κ-caseína, evidenciada por hidrolisados com massa molar abaixo de 14,4 kDa.Termos para indexação: Capra hircus, leite de cabra, papaína, pepsina, proteólise, tripsina. Evaluation of the variables that influence the enzymatic hydrolysis of Moxotó goat's milk caseinAbstract -The aim of this work was to evaluate the effects of temperature, pH, enzyme:substrate ratio (E:S), and reaction time on the enzymatic hydrolysis of Moxotó breed goat's milk casein, using different proteolytic enzymes. Enzymatic hydrolysis of the capric casein was performed using trypsin, pepsin and papain. For each enzyme, two levels of the variables were used to assess their effects on the hydrolysis of casein, using a full factorial design (2 4 ). The hydrolysis products were visualized on SDS-PAGE. The best hydrolysis degree using papain were at pH 6.5, E:S of 1:150 and 5 hours of hydrolysis at 50°C (28.17%); for trypsin, at pH 8.5, E:S of 1:150 and 5 hours at 40°C (29.55%); and for pepsin, at pH 3.0, E:S of 1:100 and 5 hours at 40°C (38.27%). Capric casein hydrolysis is affected positively by pH and reaction time, using pepsin. Significant antagonistic interactions were observed between pH and E:S, with trypsine; and between pH, temperature and reaction time, with papain. Pepsin has high α s1 , β e κ-casein hydrolysis efficiency, evidenced by the molar masses below 14.4 kDa of its products.

In order to study the biodiversity of lactic acid bacteria (LAB) and evaluate their potential for use in dairy fermentation to inhibit foodborne pathogens, we collected two types of Coalho cheese made with raw milk from an artisanal production located in Venturosa, Agreste Region in the state of Pernambuco. From 480 isolates, 210 (Gram-positive; catalase-negative; able to clot skim milk) were identified as LAB and 78 were identified at genus level. The genera found were Enterococcus (37.1%), Streptococcus (25.6%), Lactococcus (19.2%) and Leuconostoc (15.3%). The technology potential showed that most of the LAB exhibited proteolytic activity (82.9%), diacetyl production (65.7%), grown in 3, 4 and 6.5% NaCl (more than 50%), and rapidly acidified milk (52.6%) due to the production of lactic acid. The antagonistic potential showed that most LAB inhibited the growth of Staphylococcus aureus ATCC 6538 (82.89%) and Escherichia coli ATCC 25922 (88.15%), and 72.36% of the LAB presented antimicrobial activity against the two indicators. Among the Enterococcus strains, most (more than 70%) were gama-hemolitic and none produced gelatinase. This study allowed for the selection of strains with promising potential for use in dairy fermentation that could reduce the contamination of milk and cheese by foodborne pathogens.Palavras-chave: cheese, lactic acid bacteria, antagonistic and technology potential.Para estudar a biodiversidade de Bactérias Ácido Láticas (BAL) e avaliar seu potencial para a utilização como fermentos lácticos capazes de inibir patógenos alimentares, dois queijos de Coalho produzidos com leite cru foram coletados de uma unidade de produção artesanal localizada na cidade de Venturosa, Região Agreste do Estado de Pernambuco. De 480 isolados, 210 (Gram-positivos; catalase-negativo; capaz de coagular o leite desnatado) foram identificados como BAL e deste, 78 foram identificados ao nível do gênero. Os gêneros encontrados foram Enterococcus (37,1%), Streptococcus (25,6%), Lactococcus (19,2%) e Leuconostoc (15,3%). O potencial tecnológico mostrou que a maioria dos BAL exibiu atividade proteolítica (82,9%), produziu diacetil (65,7%), cresceu em 3, 4 e 6,5% NaCl (mais de 50%), acidificaram rapidamente o leite devido a produção de ácido láctico (52,6%). O potencial antagônico mostrou que a maioria das BAL inibiu o crescimento de Staphylococcus aureus ATCC 6538 (82,89%) e Escherichia coli ATCC 25922 (88,15%) e 72,36% delas, apresentaram atividade antimicrobiana contra os dois indicadores. Entre as cepas de Enterococcus, a maioria (mais de 70%) foram gama-hemolíticas e não produtoras de gelatinases. Estes estudos permitiram a seleção de cepas com potencial promissor para uso como fermentos lácteos podendo reduzir a contaminação do leite por patógenos alimentares.Keywords: queijo, bactérias ácido láticas, potencial tecnológico e antimicrobiano.

The aim of this study was to characterize the probiotic potential of 24 lactic acid bacteria (LAB) strains isolated from artisanal Coalho cheese from Pernambuco, Brazil by in vitro tests. The gastrointestinal tract (GIT) resistance, antimicrobial activity against intestinal pathogens, autoaggregation and coaggregation capacity, cell hydrophobicity, ß-galactosidase activity, deconjugate bile salt activity for the production of bile salt hydrolase (BSH), and the sensitivity to antibiotics were evaluated. Of the 24 strains, 22 remained viable to a simulated GIT. Two LAB inhibited the growth of Listeria monocytogenes and two inhibited Escherichia coli. The autoaggregation rate ranged from 27% to 96%, and the strains were able to coaggregate with Staphylococcus aureus and E. coli reaching levels between 58% and 47%, respectively. The hydrophobicity percentage ranged from 5% to 57%. Four strains were able to produce BSH. One LAB was able to produce up to 604 Miller units of ß-galactosidase. All strains were sensitive to five antibiotics and only two were resistant to vancomycin (30μg) and norfloxacin (10g). LAB strains which were able to overcome all barriers with a reduction of only one log cycle and LAB strains which were able to produce ß-galactosidase were identified by 16S rRNA sequence analysis as Lactococcus lactis subsp. Lactis, Enterococcus durans, and Enterococcus faecium. The evaluated LAB showed promising probiotic characteristics. Strains identified as L. lactis subsp. Lactis were selected for studies involving their technological potential to investigate the possible use of these microorganisms into a functional product.

No abstract