Lactobacillus buchneri strain NRRL B-30929 converts a concentrated mixture of xylose and glucose into ethanol and other products.

Lactobacillus buchneri strain NRRL B-30929 was isolated from a fuel ethanol production facility. This heterofermentative, facultative anaerobe can utilize xylose as a sole carbon source and tolerates up to 12% ethanol. Carbohydrate utilization (API, Biomerieux) and Phenotype Microarrays (PM, Biolog) analyses indicated that the strain is able to metabolize a broad spectrum of carbon sources including various monosaccharides (C5 and C6), disaccharides and oligosaccharides, with better rates under anaerobic conditions. In pH-controlled bioreactors, the bacterium consumed xylose and glucose simultaneously at high concentrations (125 g L(-1), pH 6.0). The major fermentation products were lactate (52 g L(-1)), acetate (26 g L(-1)) and ethanol (12 g L(-1)). The strain ferments glucose alone (pH 4.0) into lactate and ethanol with a molar ratio of 1.03:1. This strain will be further explored via genetic engineering for potential applications in biomass conversion.

Antimicrobial susceptibility of Lactobacillus species isolated from commercial ethanol plants.

Bacterial contamination of commercial fermentation cultures is a common and costly problem to the fuel ethanol industry. Antimicrobials such as virginiamycin (VIR) and penicillin (PEN) are frequently used to control contamination but there are little data available on the susceptibility of bacterial contaminants to these agents. A survey of bacterial contaminants from a wet-mill ethanol plant with no history of using antibiotics and a dry-grind facility that periodically doses with VIR found that the majority of contaminants were species of Lactobacillus. Thirty-seven isolates of Lactobacillus species from the wet-mill and 42 isolates from the dry-grind facility were tested for antimicrobial susceptibility using broth dilution and agar dilution methods. In general, the Lactobacillus isolates from the dry-grind plant had higher minimum inhibitory concentrations (MICs) for the tested agents than the isolates from the wet-mill facility. The MIC(90) for VIR was 4 microg/ml for the dry-grind isolates versus 0.25 microg/ml for the wet-mill isolates; and for PEN, the MIC(90)'s were >8 and 2 microg/ml for the dry-grind and wet-mill isolates, respectively. Sixteen Lactobacillus isolates from the dry-grind plant but none from the wet-mill possessed vatE, a gene that encodes a streptogramin acetyltransferase associated with resistance to virginiamycin. Despite decreased susceptibility to virginiamycin, most dry-grind isolates had MICs lower than the maximal recommended application rate of 6 ppm.

Detection of in situ derivatized peptides in microbial biofilms by laser desorption 7.87 eV postionizaton mass spectrometry.

A novel analytical method based on laser desorption postionization mass spectrometry (LDPI-MS) was developed to investigate the competence and sporulation factor-a pentapeptide of amino acid sequence ERGMT-within intact Bacillus subtilis biofilms. Derivatization of the neat ERGMT peptide with quinoline- and anthracene-based tags was separately used to lower the peptide ionization potential and permit direct ionization by 7.87-eV vacuum ultraviolet radiation. The techniques of mass shifting and selective ionization of the derivatized peptide were combined here to permit detection of ERGMT peptide within intact biofilms by LDPI-MS, without any prior extraction or chromatographic separation. Finally, imaging MS specific to the derivatized peptide was demonstrated on an intact biofilm using LDPI-MS. The presence of ERGMT in the biofilms was verified by bulk extraction/LC-MS. However, MALDI imaging MS analyses were unable to detect ERGMT within intact biofilms.

Biofilm formation by bacterial contaminants of fuel ethanol production.

Commercial fuel ethanol production facilities were previously shown to have characteristic populations of bacterial contaminants which reduce product yield and are difficult to eradicate. Bacterial contaminants were found, for the first time, to form biofilms under laboratory conditions. Fermentor samples from a commercial fuel ethanol production facility were used to inoculate a biofilm reactor and purified bacterial isolates were identified. Biofilms were composed of many of the same species present in production samples, with lactic acid bacteria predominating.