Isolamento e uso de Lactobacillus buchneri na ensilagem de capim-mombaÃa e cana-de-aÃÃcar / Isolation and use of Lactobacillus buchneri in the ensiling of MombaÃa grass and sugar cane

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

It was aimed by this work to isolate a strain of Lactobacillus buchneri in sugar cane silages for use in the ensiling of tropical forage plants. In addition, it was aimed to evaluate the influence of the species Lactobacillus buchneri on the chemical and microbiologic profile and on the aerobic stability of the silages of sugar cane (Saccharum spp.) and MombaÃa grass (Panicum maximum Jacq. cv. MombaÃa). At last, to verify if there are differences among inoculants containing bacterial strains isolated from different forage species and under distinct climatic conditions. For isolation of L. buchneri, 80 g of samples of plain sugar cane silage at 5, 20, 40 and 80 days old of fermentation mixed with 720 ml of sterile peptonized water and shaken for 20 minutes were collected. From the obtained extract, decimal dilutions of 10-1 to 10-6 and plating in MRS medium were prepared. The dishes were incubated at 30ÂC for 24-48 hours. After that period, for colony morphology, a dish and dilution that count of which was between 30 and 300 colonies was chosen. The selected isolates were purified and submitted to the specific tests: gram coloration, catalysis, motility and gas production from the glucose for classification of them at the genus level. For the identification of the species, the API system (BioMerieux, Marcy IÂToile, France) was employed. At the end, 72 isolates were obtained, all of them being classified as belonging to the genus Lactobacillus. Out of these, only 13 (18%) produced gas and were identified. In the identified isolates were found 3 different species, L. plantarum (1 isolate), L. buchneri (2 isolates) and L. brevis (8 isolates) and 2 strains were not identified. From this, it is suggested that the species L. brevis is the dominant heterofermentative bacterium during fermentation of sugar cane silage. The experiments for evaluating the fermentation profile were conducted in a completely randomized design with three silages (without inoculant and with experimental and commercial inoculants) and six times of opening of the silos (0, 3, 10, 30, 60 and 90 days). For evaluation of the aerobic stability, a completely randomized design with three replicates with splitplots in time in a scheme of the 6 x 4 type, namely, three silages (silages without inoculant and with experimental and commercial inoculants) and four aerobic evaluation times of the silages (0, 2, 8 and 10 days for MombaÃa grass and 0, 2, 4 and 6 days for sugar cane). After an ensiling period of 90 days, the silos were opened and from these were removed samples of about 3.0 kg for evaluation of the aerobic stability on the basis of temperature and chemical and microbiological modifications occurred. For the two species studied, the addition of inoculants influenced the modifications in the chemical composition of the silages along the process, where there was an interaction among the factors, the inoculated silages presented a similar profile but different from the control. At the end of the process, the chemical composition of all the silages was similar. In both, an intense utilization of the soluble carbohydrates also occurred in the first 15 days fermentation, nevertheless, the sugar cane silages presented lower pH, ammonium nitrogen and greater concentration of volatile fatty acids and lactic acid. In the MombaÃa grass silages, the two inoculants inhibited the growth of yeasts and filamentous fungi, but the commercial inoculant was more efficient. In the sugar cane silages, the population of filamentous fungi was bellow the detectable level (2.0 log cfu/g) and the one of LAB was high but that of yeasts was markedly inhibited by the inoculants as related with the highest concentration of acetic and propionic acids, resulting also into less production of ethanol in the inoculated silages. For the two species, as soon as the silos were opened, modifications in the silages were found with the increase in the populations of microorganisms resulting into reduced concentration of organic acids and increase of the pH values. The addition of L. buchneri improved the aerobic stability both for the MombaÃa grass and sugar cane silages. Nevertheless, its effect was more marked in the sugar cane silages because of the higher inhibition of yeasts as compared with the silage without any inoculants.

ASSUNTO(S)

zootecnia silagem microrganismo aerobic stability microrganism estabilidade aerÃbia fermentation innoculant inoculante silage fermentaÃÃo

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