Detection and identification of wild yeast contaminants of the industrial fuel ethanol fermentation process.

Monitoring for wild yeast contaminants is an essential component of the management of the industrial fuel ethanol manufacturing process. Here we describe the isolation and molecular identification of 24 yeast species present in bioethanol distilleries in northeast Brazil that use sugar cane juice or cane molasses as feeding substrate. Most of the yeast species could be identified readily from their unique amplification-specific polymerase chain reaction (PCR) fingerprint. Yeast of the species Dekkera bruxellensis, Candida tropicalis, Pichia galeiformis, as well as a species of Candida that belongs to the C. intermedia clade, were found to be involved in acute contamination episodes; the remaining 20 species were classified as adventitious. Additional physiologic data confirmed that the presence of these major contaminants cause decreased bioethanol yield. We conclude that PCR fingerprinting can be used in an industrial setting to monitor yeast population dynamics to early identify the presence of the most important contaminant yeasts.

Identification of Dekkera bruxellensis as a major contaminant yeast in continuous fuel ethanol fermentation.

AIMS: To identify and characterize the main contaminant yeast species detected in fuel-ethanol production plants in Northeast region of Brazil by using molecular methods. METHODS AND RESULTS: Total DNA from yeast colonies isolated from the fermentation must of industrial alcohol plants was submitted to PCR fingerprinting, D1/D2 28S rDNA sequencing and species-specific PCR analysis. The most frequent non-Saccharomyces cerevisiae isolates were identified as belonging to the species Dekkera bruxellensis, and several genetic strains could be discriminated among the isolates. The yeast population dynamics was followed on a daily basis during a whole crop harvesting period in a particular industry, showing the potential of D. bruxellensis to grow faster than S. cerevisiae in industrial conditions, causing recurrent and severe contamination episodes. CONCLUSIONS: The results showed that D. bruxellensis is one of the most important contaminant yeasts in distilleries producing fuel-ethanol from crude sugar cane juice, specially in continuous fermentation systems. SIGNIFICANCE AND IMPACT OF THE STUDY: Severe contamination of the industrial fermentation process by Dekkera yeasts has a negative impact on ethanol yield and productivity. Therefore, early detection of D. bruxellensis in industrial musts may avoid operational problems in alcohol-producing plants.

Contaminant yeast detection in industrial ethanol fermentation must by rDNA-PCR.

AIMS: The present work focuses on the possibility to use conserved primers that amplify yeast ITS1-5.8S-ITS2 ribosomal DNA locus (rDNA) to detect the presence of non-Saccharomyces cerevisiae yeast in fermentation must of bioethanol fermentation process. METHODS AND RESULTS: Total DNA was extracted from pure or mixed yeast cultures containing different cell concentrations and different contaminant/fermenting yeast concentrations and submitted to PCR. Upon improvement of detection limits and DNA extraction protocol, must samples of distillery were checked for the presence of contaminant yeast. Contaminant rDNA bands were detected only in industrial samples during contamination episodes, but not in noncontaminated must. CONCLUSIONS: The method described here could detect the presence of contaminant yeast from industrial must in eight hours after sampling. SIGNIFICANCE AND IMPACT OF THE STUDY: The improved procedure may help to avoid severe contamination episodes at fermentation industries by decreasing the detection time from 5 days to 8 h and possible quantification of contaminant yeasts that can impose economical loss to the process.

Scanning electron microscopy of the lingual mucosa of the nine-banded armadillo, Dasypus novemcinctus.

The lingual mucosa of the nine-banded armadillo, Dasypus novemcinctus, was studied by scanning electron microscopy in order to analyse its morphology. The tongue of the armadillo is long and thin, and has filiform, fungiform and vallate papillae. In the anterior part of the tongue and near the vallate papillae, single or bifurcated filiform papillae are found. The vallate papillae are located on the dorsal surface of the middle third of the tongue, and have two or four slender extremities. The fungiform papillae are elliptical or rounded, and are concentrated mainly on the tip and lateral surface of the tongue, reaching as far as the middle third of the dorsal surface. Their surfaces are flat and smooth on the dorsal side, with some taste pores. Their taste buds are located near the vallum. In the material for which freeze-cracking was used, the epithelial layer showed a characteristic mucosal structure, with many epithelial papillae containing blood vessels and bundles of collagen fibers. The basal epithelial surface of the tongue mucosa showed irregular projections that are rounded or polygonal in shape, with a depression in the center. These depressions varied in diameter.

[Taxonomic observations on Streptoverticillium griseocarneum]. / Observações taxonómicas sobre streptoverticillium griseocarneum

A strain of Streptoverticillium (IA-7527) which produces an antibiotic complex formed at least by two substances--one active against fungi and another active against bacteria--has been identified as Stv. griseocarneum. The methods and the results of the International Streptomyces Project were used. By comparing the results obtained, i.e., the description of the sample IA-7527, with ISP standard descriptions of the related species, and attributing percentual values of similarity to each corresponding item, the overall similarity between the strains compared was obtained. The main result of the study is the conclusion that the ISP descriptions of STV. EHIMENSE, Stv. kentuckense, Stv. mashuense, Stv. parvisporogenes, Stv. takataense and Stv. griseocarneum are so similar, that the cited species--and the strain ISP-5464, IMRU 3631, labeled Stv. rubireticuli--should be considered as synonyms of Stv. griseocarneum, the first species described in the group.