Effect of inoculating Pichia spp. starters on flavor formation of fermented chili pepper: Metabolomics and genomics approaches

The influence of Pichia spp. on flavor formation and metabolic pathways during chili pepper fermentation was investigated in this study. Multiple omics approaches were employed, including metabolomics analysis to identify volatile and non-volatile flavor compounds, and genomic analysis to gain insights into the underlying molecular mechanism driving flavor formation of chili peppers inoculated with Pichia spp. The results showed that inoculation with Pichia spp. accelerated fermentation process of chili peppers compared to spontaneous fermentation. Metabolomics analysis showed P. fermentans promoted characteristic terpenes [e.g., (Z)-β-ocimene and linalool], L-glutamate, gamma-aminobutyric acid, and succinate production, while P. manshurica produced more alcohols (e.g., isoamyl alcohol and phenylethyl alcohol) and phenols (e.g., 4-ethylguaiacol and 2-methoxy-4-methylphenol). Genomics analysis revealed that a substantial portion of the genes in Pichia spp. were associated with amino acid and carbohydrate metabolism. Specifically, the pathways involved in amino acid metabolism and the release of glycoside-bound aromatic compounds were identified as the primary drivers behind the unique flavor of fermented chili peppers, facilitated by Pichia spp.

Aromatic Yeasts: Interactions and Implications in Coffee Fermentation Aroma Profiles

Nontraditional yeasts prevalent in tropical agricultural fermentations such as coffee and cocoa are known to contribute to aroma profiles, yet the functional roles and interactions between the associated microbial consortia in a farm fermentation are unclear. Here, boiled green bean extract (GBE) from green coffee beans was developed as a rich screening medium to deconstruct the microbial consortia and their interactions during the fermentation of dried green coffee beans. When cultivated in coculture with S. cerevisiae on GBE, strain-specific groupings with distinct volatile organic profiles were observed for nontraditional yeasts (e.g., Hanseniaspora spp., Pichia kudriavzevii). Further changes are evident when constructed consortia composed of nontraditional yeast, S. cerevisiae, and Lactococcus lactis var. cremoris were cultured in GBE, and a comparison with abiotically acidified GBE suggests that pH plays a major role in the influence of lactic acid bacteria (LAB) on fermentation aromas. This approach represents a tool for the development of starter culture formulations to create different flavor profiles in coffee fermentation.

Non-Candida Fungal Prosthetic Joint Infections

Background: Fungal prosthetic joint infections (PJIs) are rare, especially those caused by non-Candida species. Treatment has not been fully elucidated, since a plethora of antifungal and surgical interventions have been proposed. Τhis study represents an effort to clarify the optimal management of non-Candida fungal PJIs, by reviewing all relevant published cases. Methods: A thorough review of all existing non-Candida fungal PJIs in the literature was conducted. Data regarding demographics, responsible organisms, antifungal treatment (AFT), surgical intervention, time between initial arthroplasty and onset of symptoms, and time between onset of symptoms and firm diagnosis, as well as the infection’s outcome, were evaluated. Results: Forty-two PJIs, in patients with mean age of 66.2 years, were found and reviewed. Aspergillus spp. were isolated in most cases (10; 23.8%), followed by Coccidioides spp. (7; 16.7%) and Pichiaanomala (5; 11.9%). Fluconazole was the preferred antifungal regimen (20 cases; 47.6%), followed by amphotericin B (18 cases; 42.9%), while the mean AFT duration was 9.4 months (SD = 7.06). Two-stage revision arthroplasty (TSRA) was performed in 22 cases (52.4%), with the mean time between stages being 5.2 months (SD = 2.9). The mean time between initial joint implantation and onset of symptoms was 42.1 months (SD = 50.7), while the mean time between onset of symptoms and diagnosis was 5.8 months (SD = 14.3). Conclusions: Non-Candida fungal PJIs pose a clinical challenge, demanding a multidisciplinary approach. The present review has shown that combination of TSRA separated by a 3–6-month interval and prolonged AFT has been the standard of care in the studied cases.

Adhesion of Candida spp. and Pichia spp. to Wooden Surfaces

Yeast adhesion to and biofilm formation on surfaces is present in many different environments. In food industry, biofilms may be a source of contaminations, causing food spoilage and reducing quality of products. Candida and Pichia are two common yeast genera involved in the spoilage of some food products. The aim of this study is to assess the potential of Candida and Pichia species to adhere to two types of wooden surfaces (smooth and rough), one of the materials typical for the food processing industry, and investigate the influence of surface roughness of wood on the degree of yeast adhesion. The adhesion of the cells to the wooden surfaces was determined by rinsing them from the surface, followed by methylene blue staining, and quantification after imaging under microscope by automatic counting of viable cells. The results showed that all Candida and Pichia strains were able to adhere to the wooden surfaces in a species- and strain-dependent manner. On the other hand, our data indicated that adhesion by these yeasts was not significantly affected by the roughness of the wood surfaces.

Influence of growth conditions on adhesion of yeast Candida spp. and Pichia spp. to stainless steel surfaces

An understanding of adhesion behavior of Candida and Pichia yeast under different environmental conditions is key to the development of effective preventive measures against biofilm-associated infection. Hence in this study we investigated the impact of growth medium and temperature on Candida and Pichia adherence using stainless steel (AISI 304) discs with different degrees of surface roughness (Ra = 25.20-961.9 nm), material typical for the food processing industry as well as medical devices. The adhesion of the yeast strains to stainless steel surfaces grown in Malt Extract broth (MEB) or YPD broth at three temperatures (7 °C, 37 °C, 43 °C for Candida strains and 7 °C, 27 °C, 32 °C for Pichia strains) was assessed by crystal violet staining. The results showed that the nutrient content of medium significantly influenced the quantity of adhered cells by the tested yeasts. Adhesion of C. albicans and C. glabrata on stainless steel surfaces were significantly higher in MEB, whereas for C. parapsilosis and C. krusei it was YPD broth. In the case with P. pijperi and P. membranifaciens, YPD broth was more effective in promoting adhesion than MEB. On the other hand, our data indicated that temperature is a very important factor which considerably affects the adhesion of these yeast. There was also significant difference in cell adhesion on all types of stainless steel surfaces for all tested yeast.