Seleção de cepas de bactérias do ácido lático para ensilagem da cana-de-açúcar in natura ou aditivada com glicerina acrescida de metanol e levedura metilotrófica

Abstract

Sugar cane is a forage plant with high productivity per hectare. In some situations, the ensilage is preferred compared to the daily forage harvest. Sugar cane ensilage results in high dry matter (DM) losses with a consequent reduction in the nutritional quality of the silage. The objectives of this study were to select strains of lactic acid bacteria and to evaluate the addition of glycerin plus methanol along with a methylotrophic yeast aiming at reducing DM losses, improving nutritional and microbiological quality and increasing aerobic stability of sugar cane silage. The first experiment evaluated wild strains of lactic acid bacteria (LAB) in improving the nutritional quality of cane sugar silage. The Lactobacillus hilgardii UFLA SIL51 and 52 strains stood out from the others for reducing, in average, 29.3% of the DM losses compared to the treatment without the inoculant, in addition to reducing yeast population and the ethanol concentration in the silage. Silages treated with these strains presented the highest concentration of acetic acid and 1,2 propanediol. The inoculation with L. plantarum strains reduced silage quality. The second experiment evaluated wild strains of LAB regarding the improvement of the aerobic stability of sugar cane silage, identifying the yeast species present in the silage after aerobic exposure. Inoculation with LAB strains changed the diversity of yeasts species after silo opening. The yeasts Candida diversa, C. ethanolica, Hanseniaspora opuntiae, Issatchenkia orientalis, Pichia fermentans, P. kudriavzevii, P. manshurica Schizosaccharomyces pombe, Debaryomyces etchellsii, Zygosaccharomyces bailii were identified in the silages. The treatment with the L. hilgardii UFLA SIL51 and 52 strains resulted in silages with lower temperatures and which remained unheated for a longer period. The third experiment evaluated inclusion levels of glycerin plus methanol and of L. hilgardii UFLA SIL52 in the reduction of losses and in the quality increase of sugar cane silage, and the effect of P. methanolica NCYC 1381 in reducing the methanol concentration present in the glycerin during ensilage. The use of 4% (fresh weight) of glycerin along with L. hilgardii UFLA SIL52 improved silage quality by reducing fiber and ethanol concentration and DM loss, increasing the final glycerol concentration, resulting in an increase in the energy density of the silage. These additives also increased aerobic stability. Under the conditions of the experiment, the P. methanolica NCYC1381 did not reduce the methanol concentration in the silage.