Seleção de linhagens produtoras de goma isoladas da cana-de-açucar

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The aim of this work was to isolate and select potentia1ly gum producing strains present in sugar cane. Guns are biopolymers carne 1Tom vegetal (e.g., guar gurn, carragen gum) or microbian (e.g., xantan gum, dextran gum) source. Dextran producing bacteria are 1Tequently found in damaged sugar cane. Dextran is a biopolymer that consists of a-Dglucose monomeric units. The enzyme dextransucrase, responsible for dextran synthesis, is extracellular and has sucrose as its main inductor. ln the pharmaceutical industry is where dextran has its larger applicability: low molecular weight dextran, clinical dextran, is used as blood-plasma substitute and blood flow improver. Leuconostoc mesenteroides NRRL B512F strain, used in the majority of dextran producing industries around the world, was used as reference for the isolated microorganisms selection. Damaged sugar cane sarnples, :ITom four di:fferent regions, were used as the microorganisms isolation source and the cane juice was inoculated in a 10% sucrose solid medium. Strains that had presented gummy colony formation were purmed and maintained in Litmus Milk broth at -15°C. Assays were conducted for enzime production in Erlenmyer flasks on a rotatory shaker at 150 rprn, 28::tl°C for 12 hours where each isolated microorganism was incubated in a 5% sucrose medium. The enzymatic activity of the centrifugated broth was determined by measuring :fi:uctose production rate. Gum was produced in Erlenmyer flasks containing of 15% sucrose medium on a rotatory shaker at 150 rprn, 28::tl°C for 15 hours. Etanol was added to the crude broth for gum precipitation. The strains were characterized by the produced dextran average molecular weight and by the productive capacity. The molecular weight distribution was determined by gel permeation chromatography (GPC). The sugar determination analyses were made by HPLC using an ion exchange column with amperiometric detention. Fifty six microorganisms were isolated and enzymatic activity was found in centrifugated broth of twenty eight strains. From these, tive had been selected for gum production. The activities varied 1Tom 33 to 131 UDS against 49 UDS :ITom the reference strain in the assay conditions. Among the tive selected strains, three are diplococci and produce soluble gum and the other two are streptococci and produce insoluble gum. The molecular weight distribution analysis showed that the selected strains produce high molecular weight gurn, one ofthem reaching almost 2 million Daltons

ASSUNTO(S)

microorganism isolation dextran polissacarideos microbianos enzimas extracelulares gum gomas e resinas bacterias produtoras de acido lactico dextran-sucrase

ACESSO AO ARTIGO

Documentos Relacionados