Casein digestion by Debaryomyces hansenii isolated from cheese

Co-Fermentation of Agri-Food Residues Using a Co-Culture of Yeasts as a New Bioprocess to Produce 2-Phenylethanol

Whey is a dairy residue generated during the production of cheese and yogurt. Whey contains mainly lactose and proteins, contributing to its high chemical oxygen demand (COD). Current environmental regulations request proper whey disposal to avoid environmental pollution. Whey components can be transformed by yeast into ethanol and biomolecules with aroma and flavor properties, for example, 2-phenyethanol (2PE), highly appreciated in the industry due to its organoleptic and biocidal properties. The present study aimed to valorize agri-food residues in 2PE by developing suitable bioprocess. Cheese whey was used as substrate source, whereas crab headshells, residual soy cake, and brewer's spent yeast (BSY) were used as renewable nitrogen sources for the yeasts Kluyveromyces marxianus and Debaryomyces hansenii. The BSYs promoted the growth of both yeasts and the production of 2PE in flask fermentation. The bioprocess scale-up to 2 L bioreactor allowed for obtaining a 2PE productivity of 0.04 g_2PE/L·h, twofold better productivity results compared to the literature. The bioprocess can save a treatment unit because the whey COD decreased under the detection limit of the analytical method, which is lower than environmental requirements. In this way, the bioprocess prevents environmental contamination and contributes to the circular economy of the dairy industry.

Exploring the use of sodium caseinate-assisted responsive separation for the treatment of washing effluents in shoreline oil spill response

The produced effluents after shoreline washing contain a certain number of oil droplets and further treatment is necessary. In this study, the innocuous, widely available, and biodegradable sodium caseinate (NaCas) was deployed to capture oil pollutants from oily wastewater. Oil droplets can be effectively and rapidly captured by NaCas and subsequently removed after pH-triggered separation, producing a clean supernatant with low turbidity. The removal efficiency was enhanced by increasing NaCas concentration and separation time. The salinity inhibited the oil removal by increasing the interfacial tension of NaCas and reducing their sorption sites caused by the large particle size. Humic acid negatively influenced the oil separation performance of NaCas because of the competitive sorption and enhanced repulsion force between oil and NaCas. In addition, the increasing temperature was found to augment the oil removal. Factorial analysis revealed the individual factors and two-factor interactions that had significant effects on oil removal. Biotoxicity experiments proved that NaCas can fully offset the inhibitory effect of oil on the photosynthesis of algae and thus promote algae growth. Two post-treatment methods, namely thermal treatment, and biodegradation, can be used for the post-treatment of NaCas/oil precipitation residues. The use of NaCas-assisted responsive separation in the treatment of washing effluents can help achieve a sustainable shoreline oil spill response.

Temporal differences in microbial composition of Époisses cheese rinds during ripening and storage

Époisses is a protected designation of origin smear-ripened cheese from the Burgundy region in France. It has an orange color and a strong flavor, both of which are generated by surface microorganisms. The objective of the present study was to investigate the microbial dynamics at the surface of Époisses cheese during ripening and postmanufacturing storage at low temperatures. Rind samples were analyzed by enumeration on agar plates and by 16S rRNA gene and internal transcribed spacer amplicon sequencing. During most of the ripening process, the counts of yeasts, which corresponded to the species Debaryomyces hansenii and Geotrichum candidum, were higher than those of the aerobic acid-sensitive bacteria. Debaryomyces hansenii reached a level of about 3 × 10⁸ cfu/cm², and its viability strongly decreased in the late stage of ripening and during storage at 4°C. Two of the inoculated bacterial species, Brevibacterium aurantiacum and Staphylococcus xylosus, did not establish themselves at the cheese surface. At the end of ripening, among the 18 most abundant bacterial species detected by amplicon sequencing, 14 were gram-negative, mainly from genera Psychrobacter, Vibrio, Halomonas, and Mesonia. It was hypothesized that the high moisture level of the Époisses rinds, due the humid atmosphere of the ripening rooms and to the frequent washings of the curds, favored growth of these gram-negative species. These species may be of interest for the development of efficient ripening cultures. In addition, because the orange color of Époisses cheeses could not be attributed to the growth of Brevibacterium, it would be interesting to investigate the type and origin of the pigments that confer color to this cheese.

Can cheese mites, maggots and molds enhance bioactivity? Peptidomic investigation of functional peptides in four traditional cheeses

Aside from their amino acid content, dairy proteins are valuable for their ability to carry encrypted bioactive peptides whose activities are latent until released by digestive enzymes or endogenous enzymes within the food. Peptides can possess a wide variety of functionalities, such as antibacterial, antihypertensive, and antioxidative properties, as demonstrated by in vitro and in vivo studies. This phenomenon raises the question as to what impact various traditional cheese-making processes have on the formation of bioactive peptides in the resulting products. In this study, we have profiled the naturally-occurring peptides in two hard and two soft traditional cheeses and have identified their known bioactive sequences. While past studies have typically identified fewer than 100 peptide sequences in a single cheese, we have used modern instrumentation to identify between 2900 and 4700 sequences per cheese, an increase by a factor of about 50. We demonstrated substantial variations in proteolysis and peptide formation between the interior and rind of each cheese, which we ascribed to the differences in microbial composition between these regions. We identified a total of 111 bioactive sequences among the four cheeses, with the greatest number of sequences, 89, originating from Mimolette. The most common bioactivities identified were antimicrobial and inhibition of the angiotensin-converting enzyme. This work revealed that cheese proteolysis and the resulting peptidomes are more complex than originally thought in terms of the number of peptides released, variation in peptidome across sites within a single cheese, and variation in bioactive peptides among cheese-making techniques.

The halotolerant Debaryomyces hansenii, the Cinderella of non-conventional yeasts

Debaryomyces hansenii is a halotolerant yeast with a high biotechnological potential, particularly in the food industry. However, research in this yeast is limited by its molecular peculiarities. In this review we summarize the state of the art of research in this microorganisms, describing both pros and cons. We discuss (i) its halotolerance, (ii) the molecular factors involved in saline and osmotic stress, (iii) its high gene density and ambiguous CUG decoding, and (iv) its biotechnological and medical interests. We trust that all the bottlenecks in its study will soon be overcome and D. hansenii will become a fundamental organism for food biotechnological processes. Copyright © 2016 John Wiley & Sons, Ltd.

Overview of a surface-ripened cheese community functioning by meta-omics analyses

Cheese ripening is a complex biochemical process driven by microbial communities composed of both eukaryotes and prokaryotes. Surface-ripened cheeses are widely consumed all over the world and are appreciated for their characteristic flavor. Microbial community composition has been studied for a long time on surface-ripened cheeses, but only limited knowledge has been acquired about its in situ metabolic activities. We applied metagenomic, metatranscriptomic and biochemical analyses to an experimental surface-ripened cheese composed of nine microbial species during four weeks of ripening. By combining all of the data, we were able to obtain an overview of the cheese maturation process and to better understand the metabolic activities of the different community members and their possible interactions. Furthermore, differential expression analysis was used to select a set of biomarker genes, providing a valuable tool that can be used to monitor the cheese-making process.

Debaryomyces hansenii — an extremophilic yeast with biotechnological potential

We illuminate the ecological, physiological and genetic characteristics of the yeast Debaryomyces hansenii in the view of our belief that this metabolically versatile, non-pathogenic, osmotolerant and oleaginous microorganism represents an attractive target for fundamental and applied biotechnological research. To this end, we give a broad overview of extant biotechnological procedures using D. hansenii, e.g. in the manufacture of various foods, and propose research into the heterologous synthesis of a range of fine chemicals.

The color of Brevibacterium linens depends on the yeast used for cheese deacidification

The color of smear cheeses (Muenster) is traditionally thought to be due to the bacterial flora, e.g., Brevibacterium linens. This study was carried out to evaluate indirect effects of yeast on the color of B. linens. A 60% cheese medium was desacidified with Debaryomyces hansenii or Kluyveromyces marxianus until pH 5.8 was reached. After inactivation of the yeast and addition of agar-NaCl, B. linens was inoculated on the medium surface and incubated at 12 degrees C from d 2 to 28. For each bacterial biofilm, color was evaluated by L*C*h(degrees) (brightness, chroma, hue angle) spectrocolorimetry. After d 14 (D. hansenii deacidification) and d 21 (K marxianus desacidification), the color level (as a function of all 3 factors) of B. linens biofilms became maximal and remained so until d 28. Debaryomyces hansenii 304 (LGMPA) was less efficient for deacidification than K. marxianus Laf5. However, color intensity (function of chroma only) was higher when D. hansenii was used. The yeast used had an effect on the composition of the cheese medium in relation to production and consumption of metabolites during deacidification. The results concerning color are discussed with respect to this cheese medium composition.