The sugar poured into coffee cups, cereal and favorite desserts seems so simple, so pure. The process for extracting it from unwieldy, 6-foot-tall stalks of cane? Hardly so.

That's why ARS chemist Gillian Eggleston has spent the last 13 years trying to tackle processing-related challenges in sugarcane factories. Eggleston, who works at the agency's Southern Regional Research Center in New Orleans, has already helped Louisiana's factories solve one of their stickiest issues: dextran.

Dextran is a thick, viscous material that builds up in damaged cane. It's caused by sugar-hungry bacteria that are attracted to the wounds of just-harvested or burned cane. The bacteria, Leuconostoc mesenteroides, produce the troublesome dextran as a byproduct of their feeding.

With its thick, gummy nature, dextran can clog the pipes in which cane juice is heated and clarified. Enzymes, called dextranases, must then be brought in to break down this sticky polysaccharide.

Until Eggleston's involvement, however, factory operators like Adrian Monge of Cora Texas Manufacturing Company in White Castle, La., were pretty fuzzy about which dextranase enzymes to use.

The enzymes are sold in a dizzying array of concentrations and units of measurements, leaving factory operators basically guessing about their performance. Also, little has been known about how best to use the enzymes.

Spending the bulk of her research time out of the lab and inside sugar factories, Eggleston discovered more than one sweet solution to the dextran problem.

First, she developed a simple test, known as the Eggleston titration method, for evaluating an enzyme's potency at the factory. Now, she's able to advise processors about how and where to apply the dextranase for optimal usage.

These research findings are paying off. As much as a 95 percent reduction in dextran is being seen in the five factories--of Louisiana's 12--which have adopted Eggleston's technologies.

Three kinds of lactic acid bacteria were isolated from spoiling cooked meat products stored below 10°C. They were identified as Leuconostoc mesenteroides subsp. mesenteroides, Lactococcus lactis subsp. lactis, and Leuconostoc citreum. All three strains grew well in MRS broth at 10°C. In particular, L. mesenteroides subsp. mesenteroides and L. citreum grew even at 4°C, and their doubling times were 23.6 and 51.5 h, respectively. On the other hand, although the bacteria were initially below the detection limit (<10 CFU/g) in model cooked meat products, the bacterial counts increased to 10⁸ CFU/g at 10°C after 7 to 12 days.

The micrographs illustrating this page were obtained by scanning electron microscopy (SEM). As indicated at the bottom of this site, the four strains of Leuconostoc spp. bacteria were provided from institutional collections. Leuconostocs may be found in various environments.

As this WinWord DOC file explains, the genus Leuconostoc belongs to the group of lactic acid bacteria. They are a group of related Gram-positive, non-sporulating bacteria that produce lactic acid as a result of carbohydrate fermentation. Milk provides a good substrate for microorganisms that further improve nutrition, texture and flavor characteristics of a wide variety of foods. Lactic acid bacteria are used in the production of fermented food products, such as yogurt (Streptococcus spp. and Lactobacillus spp. and other milk products (Lactococcus spp.), and sausages. However, fermented milk products also contain Leuconostoc spp. bacteria (e.g., L. cremoris, L. citrovorum (L. mesenteroides subsp. cremoris, and L. dextranicum) which impart characteristic flavour. They are used as part of bacterial starter cultures needed in the manufacture of dairy products. L. mesenteroides subsp. cremoris is used in cultured buttermilk and cultured sour cream. A variety of Leuconostoc strains is present in kefir.

Like the lactic acid bacteria, leuconostocs need complex media due to their multiple demands for amino acids, peptides, carbohydrates, vitamins and metallic ions. They represent about 12% of lactic acid bacteria isolated from various ecosystems, mostly from plant materials. Some may be isolated from the surfaces of a wide range of healthy vegetables and fruits, including grapes.

Sauerkraut fermentation relies on naturally occurring Leuconostoc spp. bacteria present on fresh cabbage leaves. Leuconostoc mesenteroides is the bacterium associated with the sauerkraut and pickle fermentations. It initiates the desirable lactic acid production in these products. Translated from German, "sauerkraut" means "sour cabbage". Lactic acid and the kitchen salt used produce an environment more favourable for Leuconostoc than other bacteria and, consequently, unwelcome coliform bacteria rapidly decline. Additional probiotic microrganisms are also involved in the production of sauerkraut. They multiply in large quantities in the juice. On sauerkraut particles the microorganisms may be found congregated at the leaf stomata as shown below.