Orientador: Adilma Regina Pippa ScampariniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de AlimentosResumo: A determinação da estrutura química de polissacarídeos tem sido objeto constante de estudo em todo o mundo. Através da determinação das características estruturais de um polissacarídeo é possível definir qual é o seu campo de aplicação, quais as suas possíveis funções em determinados produtos, e qual a sua atuação no comportamento reológico de uma substância. Neste trabalho foram determinadas as características estruturais do polissacarídeo PS-32, obtido da fermentação aeróbica da bactéria Beijerinckia sp (cepa 32) isolada do solo cultivado com cana de açúcar em Ribeirão Preto, S.P, por VENDRUSCOLO, 1995. As bactérias do gênero Beijerinckia sp são encontradas frequentemente em solos de clima tropical e se apresentam na forma de bastonetes Gram-negativos, sendo aeróbicas, catalase-positivas e fixadoras de nitrogênio molecular. Para a produção do biopolímero PS-32 foi utilizado um meio de fermentação contendo 5% de sacarose como fonte de carbono, 0,05% de MgS04, 0,01% de K2HPO4, 0,05% de KH2PO4 e 0,5% de triptose que foi inoculado com 5% de meio YM contendo a bactéria Beijerinckia sp. O caldo de fermentação permaneceu por 72 horas sendo aerado com agitação de 200 rpm a 25°C. Após este período, o caldo de fermentação foi centrifugado para retirada das células e o polissacarídeo foi recuperado por precipitação com etanol, seco em estufa a vácuo e triturado em moinho de bolas, rendendo de 7 a 9g de polissacarídeo/L de caldo. Após este estágio, a proteína presente nas soluções do polissacarídeo foi retirada por hidrólise com papaína e as soluções sofreram sucessivas diálises contra água destilada, até purificação total. As caracteríticas da estrutura do polissacarídeo PS-32 foram estudadas utilizando técnicas cromatográficas acopladas ao espectrômetro de massa e ressonância magnética nuclear de 1H e 13C. ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digitalAbstract: The determination of polysaccharides chemical structure has been studied all over the world. Through this determination it is possible to define where the polysaccharide could be employed, which its possible functions in différents products are and how it will affect the rheological behaviour of a substance. In this work the structural characteristics of PS-32 polysaccharide obtained from aerobic fermentation of Beijerinckia sp (strain 32) bacterium, isolated from soil cultivated with sugar cane in Ribeirão Preto, S.P. by VENDRUSCOLO, 1995 were studied. Beijerinckia sp bacteria are often found in tropical climate and show the following characteristics: gram-negative rods, aerobic, catalase-positive and chemoorganotrophic. For PS-32 polysaccharide production it was used a medium containing sucrose 5%, MgSO4, 0.05%, K2HPO4, 0.01%, KH2PO4 0.05% and tryptose 0.5%. This media was inoculated with 5% of YM browth containing Beijerinckia sp. The fermentation browth was kept during 72 hours at 200 rpm and 25°C. After this period, the browth was centrifugated in order to separate the cells. The polysaccharide was recovered by ethanol precipitation, dried under vacuum and powdered. This procedure yielded 7-9 grams of polysaccharide/litre of browth. After this step, the protein present in polysaccharide solution was eliminated by papain hydrolysis. The polysaccharide solution was dialysed against distillated water, untyl totaly purified. PS-32 polysaccharide structure features were studied by high performance liquid chromatography, gas-liquid chromatography-mass spectrometry, nuclear magnetic ressonance of 1H and 13C and IR. HPLC was used in order to determinate and quantificate monosaccharides present in PS-32 polysaccharide. Therefore, were tested two kinds of hydrolysis: (i) 1M HC1, 70°C, 16 h and (ii) 2N TFA, 100°C, 16 h. It was used a Shimadzu Co. HPLC and hydrolysates were analysed in a 7,9 mm x 30 cm column (SCR-101-P, Shimadzu Co.), with sulfonated polystyrene bonded to Pb+2 cation (ligand exchange) and gel filtration separation. The separation was based in the stability of complex between hidroxyl groups and Pb+2 cation, too. The column temperature was 80°C. It was used ultrapure water as mobile phase, with flow of 0,6 mL/minute. An automatic injector of samples was used. The refractive index detector was used to detect sugars. Sugars were identified by the retention time of corresponded standards and confirmed by mass spectrometry. Using calibration curves with external standards it was quantified glucose:galactose:fucose at the proportion of 3:1:3, respectively. TFA hydrolysate showed best results. In order to confirm the sugars composition in PS-32 polysaccharide and determinate glycosidic linkages positions between these sugar residues, PS-32 polysaccharide was methylated according to HAKOMORI, 1964, hydrolysated, reduced and acetylated. It was obtained acetalic alditols parcialy methylated. This alditols were analysed in a Shimadzu Co. GC-MS. It was used a fused-silic bonded capillary column DB-5, 22 mm X 50 m, split of 1/100 and a temperature program: 130°C during the 5 initial minutes, arising to 300°C, 7°C/minute. Note: The complete abstract is available with the full electronic documentMestradoMestre em Ciencia de Alimentos