No abstract

Glucoamylase (EC 3.2.1.3) hydrolyzes polysaccharides from the nonreducing chain ends by cleaving α‐1,4 and α‐1,6 glycosidic bonds consecutively. Glucoamylases are used mainly in the production glucose syrup, high fructose corn syrup, and in whole grain and starch hydrolysis for alcohol production. This paper reviews the status of glucoamylases with respect to microbial sources, biochemical and physical properties. Methods used to assay glucoamylase activity are also compared, with reference being made to the specificity of spectrophotometric methods in detecting end products of the enzyme action. Commercial glucoamylases and development of immobilization techniques are discussed. Also, structural analysis of glucoamylase and the main amino acids involved in catalysis and starch binding are emphasized. The cloning of the glucoamylase gene in Saccharomyces cerevisiae for the brewing of low calorie beer is presented. This review highlights the use of glucoamylase in the food industry.

Enzymes offer potential for many exciting applications for the improvement of foods. There is still, however, a long way to go in realizing this potential. Economic factors such as achievement of optimum yields and efficient recovery of desired protein are the main deterrents in the use of enzymes. Changing values in society with respect to recombinant DNA and protein engineering technologies and the growing need to explore all alternative food sources may in time make enzyme applications more attractive to the food industry. Research is continuing on the commercially viable enzymes in use today to improve various properties such as thermostabilities, specificities, and catalytic efficiencies. New and unique enzymes continue to be developed for use in enzymatic reactions to produce food ingredients by hydrolysis, synthesis, or biocatalysis. An aggressive approach is needed to open new opportunities for enzyme applications that can benefit the food industry.

An intracellular glucoamylase (E.C. 3.2.1.3) was purified to homogeneity from Lactobacillus amylovorus on a Fast Protein liquid chromatography System (FPLC) with a Mono Q ion-exchanger and two Superose 12 gel filtration columns arranged in series. The enzyme activity was quantified with a specific, chromogenic substrate, p-nitrophenyl-beta-maltoside. Preparative gel electrophoresis was then used to further purify active enzyme fractions. Native polyacrylamide gel electrophoresis (Native-PAGE) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the purified enzyme showed a single protein band of molecular weight 47 kDa. Glucoamylase activity of the purified protein was confirmed by its ability to degrade starch on a 0.025% starch-polyacrylamide gel stained with I2/KI. Glucoamylase exhibited optimum catalytic activity at pH 6.0 and 45 degrees C, and the enzyme had an isoelectric point near 4.39. The glucoamylase contained high levels of hydrophilic amino acids, comparable to fungal glucoamylases.

Muscadine grapes (Vitis rotundifolia michx.) are highly perishable, with a short harvest season. The objective of this study was to enhance the commercial viability of muscadine grapes by developing harvesting and handling systems through interstate shipment studies, using sulfur dioxide and/or polyethylene overwrap treatments. Cultivars Fry, Summit and Granny Val from Florida, Arkansas and Mississippi, respectively, were shipped from each region to the other in refrigerated trucks for subsequent storage at OC and evaluation at 0, 2, 4 and 6 weeks. Biochemical properties: pH, titratable acidity and degrees Brix, remained fairly constant with time for all cultivars, under all treatments. The cultivar, Granny Val, which was shipped, wrinkled after 2 weeks' storage, but maintained 6 weeks' shelf‐life in the in‐house study. ‘Summit’ shelf‐life was increased to 4 weeks with SO2 treatment at all test sites while ‘Fry’ became bleached by SO2. The shelf‐life of ‘Fry’ was 6 weeks in the in‐house study using