Isolation of Clavispora lusitaniae from the Oral Cavity of Immunocompetent Young Adults from the North of Mexico.

The human oral cavity is normally colonized by microorganisms including bacteria, fungi, archaea, viruses and protozoa. The aim of this study was to determine the frequency of Candida spp., in de oral cavity in a group of medical students from the north of Mexico. Oral sample were obtained from 240 healthy students. The specimens were analyzed by traditional microbiology cultures and DNA sequencing. Candida spp., grew in Sabouraud dextrose agar from 57 samples and subsequently were isolated and phenotyped. The definitive identification to the species level was done by sequence analysis. The yeasts were identified as follow: 28 Clavispora lusitaniae, 20 Candida albicans, 5 Pichia kudriavzevii and 4 Candida parapsilosis. Our findings revealed that 23.75% of the healthy population has a potential pathogen in their mouth. Surprisingly, C. albicans is not the predominant yeast; instead other non-Candida species are the colonizers of the oral cavity as normal microbiota. C. lusitaniae is considered an emerging opportunistic pathogen in immunosuppressive patients. This paper pretends to highlight the presence of this yeast in the oral cavity in immunocompetent young adults. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-023-01145-x.

Fermentation performance of a Mexican native Clavispora lusitaniae strain for xylitol and ethanol production from xylose, glucose and cellobiose.

Lignocellulose hydrolysates are rich in fermentable sugars such as xylose, cellobiose and glucose, with high potential in the biotechnology industry to obtain bioproducts of higher economic value. Thus, it is important to search for and study new yeast strains that co-consume these sugars to achieve better yields and productivity in the processes. The yeast Clavispora lusitaniae CDBB-L-2031, a native strain isolated from mezcal must, was studied under various culture conditions to potentially produce ethanol and xylitol due to its ability to assimilate xylose, cellobiose and glucose. This yeast produced ethanol under microaerobic conditions with yields of 0.451 gethanol/gglucose and 0.344 gethanol/gcellobiose, when grown on 1% glucose or cellobiose, respectively. In mixtures (0.5% each) of glucose:xylose and glucose:xylose:cellobiose the yields were 0.367 gethanol/gGX and 0. 380 gethanol/gGXC, respectively. Likewise, in identical conditions, C. lusitaniae produced xylitol from xylose with a yield of 0.421 gxylitol/gxylose. In 5% glucose or xylose, this yeast had better ethanol and xylitol titers and yields, respectively. However, glucose negatively affected xylitol production in the mixture of both sugars (3% each), producing only ethanol. Xylose reductase (XR) and xylitol dehydrogenase (XDH) activities were evaluated in cultures growing on xylose or glucose, obtaining the highest values in cultures on xylose at 8 h (25.9 and 6.22 mU/mg, respectively). While in glucose cultures, XR and XDH activities were detected once this substrate was consumed (4.06 and 3.32 mU/mg, respectively). Finally, the XYL1 and XYL2 genes encoding xylose reductase and xylitol dehydrogenase, respectively, were up-regulated by xylose, whereas glucose down-regulated their expression.

Protection of Citrus Fruits from Postharvest Infection with Penicillium digitatum and Degradation of Patulin by Biocontrol Yeast Clavispora lusitaniae 146.

Fungal rots are one of the main causes of large economic losses and deterioration in the quality and nutrient composition of fruits during the postharvest stage. The yeast Clavispora lusitaniae 146 has previously been shown to efficiently protect lemons from green mold caused by Penicillium digitatum. In this work, the effect of yeast concentration and exposure time on biocontrol efficiency was assessed; the protection of various citrus fruits against P. digitatum by C. lusitaniae 146 was evaluated; the ability of strain 146 to degrade mycotoxin patulin was tested; and the effect of the treatment on the sensory properties of fruits was determined. An efficient protection of lemons was achieved after minimum exposure to a relatively low yeast cell concentration. Apart from lemons, the yeast prevented green mold in grapefruits, mandarins, oranges, and tangerines, implying that it can be used as a broad-range biocontrol agent in citrus. The ability to degrade patulin indicated that strain 146 may be suitable for the control of further Penicillium species. Yeast treatment did not alter the sensory perception of the aroma of fruits. These results corroborate the potential of C. lusitaniae 146 for the control of postharvest diseases of citrus fruits and indicate its suitability for industrial-scale fruit processing.

In vitro lytic activity and antifungal susceptibility of infrequently isolated yeasts.

Non-albicans Candida species have acquired relevance in the last decades as a cause of serious disease. The virulence factors and antifungal susceptibility of these rare pathogens remain largely unrecognized. We examined a total of 50 yeast isolates corresponding to 11 different infrequently isolated yeast species for their in vitro enzymatic profile and susceptibility pattern as first-line antifungals. We found aspartyl protease activity for 100% of the isolates tested as well as variable DNAse, hemolysin, phospholipase and esterase activities. All strains had low MICs for amphotericin B and showed a variable response to fluconazole (0.125-32 µg/mL) and the echinocandins tested (0.25-> 8 µg/mL).