RT-PCR amplification of a Rhizopus oryzae lactate dehydrogenase gene fragment

Rhizopus oryzae - Ancient microbial resource with importance in modern food industry

Filamentous fungi are microorganisms widely known for their diverse biochemical features. Fungi can efficiently invade a wide variety of substrates under operational conditions producing numerous bioproducts of interest, such as enzymes, organic acids, aromatic compounds and colorants. An additional interesting characteristic of some fungi is their safety classification for different uses, which guarantees that the bioproducts obtained from them do not contain any toxic component deleterious to humans. Rhizopus oryzae is among this group of fungi and is classified as a GRAS filamentous fungus, commonly used for production of some oriental traditional foods. It is mainly recognized as a good producer of lactic acid; however, its potential for other biotechnological processes is under study. This review analyzes and discusses the current scientific and technical contributions which may maximize the potential of R. oryzae as a producer of different compounds of industrial interest.

Adsorption of organic matter at mineral/water interfaces: 7. ATR-FTIR and quantum chemical study of lactate interactions with hematite nanoparticles

The interaction of the l-lactate ion ( l-CH3CH(OH)COO(-), lact(-1)) with hematite (alpha-Fe2O3) nanoparticles (average diameter 11 nm) in the presence of bulk water at pH 5 and 25 degrees C was examined using a combination of (1) macroscopic uptake measurements, (2) in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and (3) density functional theory modeling at the B3LYP/6-31+G* level. Uptake measurements indicate that increasing [ lact(-1)]aq results in an increase in lact(-1) uptake and a concomitant increase in Fe(III) release as a result of the dissolution of the hematite nanoparticles. The ATR-FTIR spectra of aqueous lact(-1) and lact(-1) adsorbed onto hematite nanoparticles at coverages ranging from 0.52 to 5.21 micromol/m2 showed significant differences in peak positions and shapes of carboxyl group stretches. On the basis of Gaussian fits of the spectra, we conclude that lact(-1) is present as both outer-sphere and inner-sphere complexes on the hematite nanoparticles. No significant dependence of the extent of lact(-1) adsorption on background electrolyte concentration was found, suggesting that the dominant adsorption mode for lact(-1) is inner sphere under these conditions. On the basis of quantum chemical modeling, we suggest that inner-sphere complexes of lact(-1) adsorbed on hematite nanoparticles occur dominantly as monodentate, mononuclear complexes with the hydroxyl functional group pointing away from the Fe(III) center.

Isolation and molecular characterization of Shewanella sp. G5, a producer of cold-active beta-D-glucosidases

beta -Glucosidase is a highly desired glycosidase, especially for hydrolysis of glycoconjugated precursors in musts and wines for the release of active aromatic compounds. A Shewanella sp. G5 strain was isolated from the intestinal content of benthonic organism (Munida subrrugosa) from different coastal areas of the Beagle Channel, Tierra del Fuego (Argentina). This marine bacterium was able to grow at a temperature range between 4 to 20 degrees C using different beta-glycoside substrates, such as cellobiose, as carbon source. In this work, the Shewanella sp. G5 strain exhibited high beta-glucosidase activity on plate at low temperature (4 and 20 degrees C). Two genes encoding different cold-active beta-glucosidases were amplified and sequenced and the nucleotide sequences were submitted to the GenBank. 16S rDNA and gyrB gene sequences were used for the molecular characterization of Shewanella sp. G5.

Evaluation of intra-specific diversities in Oenococcus oeni through analysis of genomic and expressed DNA

In winemaking Oenococcus (O.) oeni is the most frequent species of lactic acid bacteria (LAB) associated with malolactic fermentation (MLF). Several studies have demonstrated that O. oeni is a quite homogeneous species and strains are difficult to differentiate especially when isolates from the same region are analyzed. In this study, the molecular biodiversity of O. oeni isolated from wines of the same region (Aglianico produced in Basilicata Region, Southern Italy) was evaluated with the aim of designing a molecular approach for discrimination and characterization of the isolates at the strain level. Three molecular techniques were applied: random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR), restriction endonucleases analysis-pulsed field gel electrophoresis (REA-PFGE) and differential display PCR (DD-PCR). The results obtained by RAPD-PCR confirmed the difficulty in differentiating isolates. By means of REA-PFGE a higher polymorphism, often related to the origin (winery) of strains, was revealed. However, on analyzing strains isolated from the same winery, only in some cases was more than one REA-PFGE pattern obtained. By analyzing dendrograms constructed on the basis of DD-PCR profiles differentiation of strains isolated from the same winery, in some cases, could be accomplished. The reliability of the DD-PCR in the differentiation of closely related strains suggests that this method could represent an alternative and/or additional tool to other molecular methods, such as REA-PFGE, for fine characterization of oenococcal strains.

Production of lactic acid and fungal biomass by Rhizopus fungi from food processing waste streams

This study proposed a novel waste utilization bioprocess for production of lactic acid and fungal biomass from waste streams by fungal species of Rhizopus arrhizus 36017 and R. oryzae 2062. The lactic acid and fungal biomass were produced in a single-stage simultaneous saccharification and fermentation process using potato, corn, wheat and pineapple waste streams as production media. R. arrhizus 36017 gave a high lactic acid yield up to 0.94-0.97 g/g of starch or sugars associated with 4-5 g/l of fungal biomass produced, while 17-19 g/l fungal biomass with a lactic acid yield of 0.65-0.76 g/g was produced by the R. oryzae 2062 in 36-48 h fermentation. Supplementation of 2 g/l of ammonium sulfate, yeast extract and peptone stimulated an increase in 8-15% lactic acid yield and 10-20% fungal biomass.

Direct fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of direct fermentation for lactic acid production by fungal species of Rhizopus arrhizus 3,6017 and Rhizopus oryzae 2,062 was studied with respect to growth pH, temperature and substrate. The direct fermentation was characterized by starch hydrolysis, accumulation of reducing sugar, and production of lactic acid and fungal biomass. Starch hydrolysis, reducing sugar accumulation, biomass formation and lactic acid production were affected with the variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.87-0.97 g/g starch associated with 1.5-2.0 g/l fungal biomass produced in 36 h fermentation. R. arrhizus 3,6017 had a higher capacity to produce lactic acid, while R. oryzae 2,062 produced more fungal biomass under similar conditions.