Purification and Properties of Yeast Proteases Secreted by Wickerhamomyces anomalus 227 and Metschnikovia pulcherrima 446 during Growth in a White Grape Juice

A fast microbial nitrogen-assimilation technology enhances nitrogen migration and single-cell-protein production in high-ammonia piggery wastewater

Conventional methods, such as freshwater dilution and ammonia stripping, have been widely employed for microalgae-based piggery wastewater (PW) treatment, but they cause high freshwater consumption and intensive ammonia loss, respectively. This present work developed a novel fast microbial nitrogen-assimilation technology by integrating nitrogen starvation, zeolite-based adsorption, pH control, and co-culture of microalgae-yeast for the PW treatment. Among them, the nitrogen starvation accelerated the nitrogen removal and shortened the treatment period, but it could not improve the tolerance level of microalgal cells to ammonia toxicity based on oxidative stress. Therefore, zeolite was added to reduce the initial total ammonia-nitrogen concentration to around 300 mg/L by ammonia adsorption. Slowly releasing ammonia at the later phase maintained the total ammonia-nitrogen concentration in the PW. However, the pH increase could cause lots of ammonia loss air and pollution and inhibit the desorption of ammonia from zeolite and the growth and metabolism of microalgae during the microalgae cultivation. Thus, the highest biomass yield (3.25 g/L) and nitrogen recovery ratio (40.31%) were achieved when the pH of PW was controlled at 6.0. After combining the co-cultivation of microalgae-yeast, the carbon-nitrogen co-assimilation and the alleviation of pH fluctuation further enhanced the nutrient removal and nitrogen migration to high-protein biomass. Consequently, the fast microbial nitrogen-assimilation technology can help update the industrial system for high-ammonia wastewater treatment by improving the treatment and nitrogen recovery rates.

Pleurotus pulmonarius: a protease-producing white rot fungus in lignocellulosic residues

The production of proteases by white rot fungi, such as those of the genus Pleurotus, is related to the degradation of wood proteins, the substrate on which these fungi grow in the environment. From the point of view of production, they are still little explored for this purpose. A selection of agro-industrial residues highlighted corn bagasse as the best substrate for solid-state protease production using the basidiomycete Pleurotus pulmonarius. The enzyme production was maximized through a factorial design, where the enzyme activity increased from 137.8 ± 1.9 to 234.1 ± 2.7 U/mL. Factors such as temperature stability, pH, and chemical reagents were evaluated. The optimum temperature was 45 °C, showing low thermal stability at higher temperatures. The enzyme inhibition occurred by Mn²⁺ (50.3%) and Ba²⁺ (76.4%); SDS strongly inhibited the activity (82.4%), while pepstatin A partially inhibited (56%), suggesting an aspartic protease character. Regarding pH, the highest protease activity was obtained at pH 5.5. Partial characterization resulted in apparent values of the K_M and V_max constants of 0.61 mg/mL and 1.79 mM/min, respectively.

The Ability of the Yeast Wickerhamomyces anomalus to Hydrolyze Immunogenic Wheat Gliadin Proteins

Gliadins proteins make up around 30% of total wheat flour proteins. They are involved in many immune disorders affecting an increasing number of people who eat foods made with wheat flour. The triggering factor is the accumulation in the gut of immunogenic peptides derived from incomplete degradation of gliadins by gastric proteases. Previous research has revealed the effectiveness of sourdough-fermentation technology or related lactic acid bacteria in reducing wheat flour allergenic proteins. However, there are no single yeast cultures for producing reduced allergenicity wheat products. This study evaluated sourdough-related yeast Wickerhamomyces anomalus strains for their ability to hydrolyze gliadin proteins. All yeast strains were able to degrade gliadins and use them as carbon and nitrogen sources. The proliferation of the yeast strains depended on the gliadin addition; complete hydrolysis was observed after 24 h. The strain showing higher proteolytic activity fermented, acceptably wheat flour dough. The gliadin content of the leavened dough was reduced by 50%. Bread made from the W. anomalus-fermented dough showed a 78% reduction in immunogenic α-gliadins. 50% of the decrease was attributed to the proteolytic activity of the yeast cells, and the other 35% to the baking process. These results show the potential of the yeast W. anomalus as a starter for reducing immunogenicity wheat products.

Organic Farm Bedded Pack System Microbiomes: A Case Study with Comparisons to Similar and Different Bedded Packs

Animal housing and bedding materials influence cow and farm worker exposure to microbial pathogens, biocontrol agents, and/or allergens. This case study represents an effort to characterize the bacterial and fungal community of bedding systems using an amplicon sequencing approach supplemented with the ecological assessment of cultured Trichocomaceae isolates (focusing on Penicillium and Aspergillus species) and yeasts (Saccharomycetales). Bedding from five certified organic dairy farms in northern Vermont USA were sampled monthly between October 2015 and May 2016. Additional herd level samples from bulk tank milk and two bedding types were collected from two farms to collect fungal isolates for culturing and ecology. Most of the microorganisms in cattle bedding were microbial decomposers (saprophytes) or coprophiles, on account of the bedding being composed of dead plant matter, cattle feces, and urine. Composition of bacterial and fungal communities exhibited distinct patterns of ecological succession measured through time and by bedding depth. Community composition patterns were related to management practices and choice of bedding material. Aspergillus and Penicillium species exhibited niche differentiation expressed as differential substrate requirements; however, they generally exhibited traits of early colonizers of bedding substrates, typically rich in carbon and low in nitrogen. Pichia kudriavzevii was the most prevalent species cultured from milk and bedding. P. kudriavzevii produced protease and its abundance directly related to temperature. The choice of bedding and its management represent a potential opportunity to curate the microbial community of the housing environment.

Non-Saccharomyces in Winemaking: Source of Mannoproteins, Nitrogen, Enzymes, and Antimicrobial Compounds

Traditionally, non-Saccharomyces yeasts have been considered contaminants because of their high production of metabolites with negative connotations in wine. This aspect has been changing in recent years due to an increased interest in the use of these yeasts in the winemaking process. The majority of these yeasts have a low fermentation power, being used in mixed fermentations with Saccharomyces cerevisiae due to their ability to produce metabolites of enological interest, such as glycerol, fatty acids, organic acids, esters, higher alcohols, stable pigments, among others. Additionally, existing literature reports various compounds derived from the cellular structure of non-Saccharomyces yeasts with benefits in the winemaking process, such as polysaccharides, proteins, enzymes, peptides, amino acids, or antimicrobial compounds, some of which, besides contributing to improving the quality of the wine, can be used as a source of nitrogen for the fermentation yeasts. These compounds can be produced exogenously, and later incorporated into the winemaking process, or be uptake directly by S. cerevisiae from the fermentation medium after their release via lysis of non-Saccharomyces yeasts in sequential fermentations.

Into the wild: new yeast genomes from natural environments and new tools for their analysis

Genomic studies of yeasts from the wild have increased considerably in the past few years. This revolution has been fueled by advances in high-throughput sequencing technologies and a better understanding of yeast ecology and phylogeography, especially for biotechnologically important species. The present review aims to first introduce new bioinformatic tools available for the generation and analysis of yeast genomes. We also assess the accumulated genomic data of wild isolates of industrially relevant species, such as Saccharomyces spp., which provide unique opportunities to further investigate the domestication processes associated with the fermentation industry and opportunistic pathogenesis. The availability of genome sequences of other less conventional yeasts obtained from the wild has also increased substantially, including representatives of the phyla Ascomycota (e.g. Hanseniaspora) and Basidiomycota (e.g. Phaffia). Here, we review salient examples of both fundamental and applied research that demonstrate the importance of continuing to sequence and analyze genomes of wild yeasts.

Biocatalysis in the winemaking industry: Challenges and opportunities for immobilized enzymes

Enzymes are powerful catalysts already being used in a large number of industrial processes. Impressive advantages in enzyme catalysts improvement have occurred in recent years aiming to improve their performance under harsh operation conditions far away from those of their cellular habitat. Production levels of the winemaking industry have experienced a remarkable increase, and technological innovations have been introduced for increasing the efficiency at different process steps or for improving wine quality, which is a key issue in this industry. Enzymes, such as pectinases and proteases, have been traditionally used, and others, such as glycosidases, have been more recently introduced in the modern wine industry, and many dedicated studies refer to the improvement of enzyme performance under winemaking conditions. Within this framework, a thorough review on the role of enzymes in winemaking is presented, with special emphasis on the use of immobilized enzymes as a significant strategy for catalyst improvement within an industry in which enzymes play important roles that are to be reinforced paralleling innovation.

Assessment of microbial quality and health risks associated with traditional rice wine starter Xaj-pitha of Assam, India: a step towards defined and controlled fermentation

This study reports the microbial quality of ethnic starter culture Xaj-pitha used for rice wine fermentation in Assam. Here, we collected 60 Xaj-pitha samples belonging to Ahom community of the state and enumerated the microorganisms using spread plate technique. Illumina-based whole genome shotgun sequencing detected the presence of microbial contaminants like Acidovorax, Herbaspirillum, Methylobacterium, Pantoea, Pseudomonas, Stenotrophomonas, Staphylococcus, Micrococcus, Acinetobacter, etc. Presence of major health hazards associated with spontaneous rice wine fermentation necessitated method optimization through the development of a defined mixed starter culture. For this, functionally important α-amylase producers viz., Penicillium sp. ABTSJ23, Rhizopus oryzae ABTSJ63, Mucor guilliermondii ABTSJ72 and Amylomyces rouxii ABTSJ82 and eight yeasts viz., Saccharomyces cerevisiae ABTY1J, ABTY1S, ADJ5 & ADJ1, Wickerhamomyces anomalus ADJ2, Saccharomycopsis malanga ADJ3, Saccharomycopsis fibuligera ADJ4 and Saccharomycopsis malanga ADJ6 were retrieved using appropriate media. All the mould cultures tested negative for aflotoxins production. Among the yeasts, Saccharomyces cerevisiae ABTY1S and ADJ1 decarboxylated lysine HCl and tyramine HCl, respectively, indicating their biogenic amine production ability. For defined mixed starter culture, Amylomyces rouxii ABT82 with α-amylase (5.92 U/ml) and glucoamylase (7.50 U/ml) activities was selected as fungal partner; while Saccharomycopsis fibuligera ADJ4 and Saccharomyces cerevisiae ABT-Y1J with high ethanol production (up to 10.11% and 9.88% v/v, respectively) were selected as yeast partners. The mixed culture was able to produce high amount of glucose, ethanol and liquid (glucose 10.91% w/v; ethanol 7.5% w/v; liquid 51.0% w/v). Therefore, this study demonstrated the efficiency of mixed starter cultures for safe and controlled rice wine production.

Carotenoid-producing yeasts: Identification and Characteristics of Environmental Isolates with a Valuable Extracellular Enzymatic Activity

Sixteen cold-adapted reddish-pigmented yeast strains were obtained from environmental samples. According to the PCR-based detection of classical yeast markers combined with phylogenetic studies, the yeasts belong mainly to the genera Rhodotorula, Sporobolomyces and Cystobasidium, all within the subphylum Pucciniomycotina. All strains produced carotenoids within a 0.25–10.33 mg/L range under non-optimized conditions. Noteworthily, among them, representatives of the Cystobasidium genus were found; of particular value are the strains C. laryngis and C. psychroaquaticum, poorly described in the literature to date. Interestingly, carotenoid production with representatives of Cystobasidium was improved 1.8- to 10-fold at reduced temperature. As expected, most of the isolated yeasts biosynthesized extracellular lipases, but within them also one proteolytic and four cellulolytic strains were revealed. We succeeded in isolating strain Cystofilobasidium macerans WUT145 with extraordinarily high cellulolytic activity at 22°C (66.23 ± 0.15 µmol/mg protein·min) that is described here for the first time. Consequently, a set of yeasts capable of producing both carotenoids and extracellular enzymes was identified. Taking into account those abilities, the strains might be applicable for a development of carotenoids production on an agro-industrial waste, e.g., lignocellulose.

Understanding the regulation of extracellular protease gene expression in fungi: a key step towards their biotechnological applications

The secretion of proteases by certain species of yeast and filamentous fungi is of importance not only for their biological function and survival, but also for their biotechnological application to various processes in the food, beverage, and bioprocessing industries. A key step towards understanding the role that these organisms play in their environment, and how their protease-secreting ability may be optimally utilised through industrial applications, involves an evaluation of those factors which influence protease production. The objective of this review is to provide an overview of the findings from investigations directed at elucidating the regulatory mechanisms underlying extracellular protease secretion in yeast and filamentous fungi, and the environmental stimuli that elicit these responses. The influence of nitrogen-, carbon-, and sulphur-containing compounds, as well as proteins, temperature, and pH, on extracellular protease regulation, which is frequently exerted at the transcriptional level, is discussed in particular depth. Protease-secreting organisms of biotechnological interest are also presented in this context, in an effort to explore the areas of industrial significance that could possibly benefit from such knowledge. In this way, the establishment of a platform of existing knowledge regarding fungal protease regulation is attempted, with the particular goal of aiding in the practical application of these organisms to processes that require secretion of this enzyme.

Challenges of the Non-Conventional Yeast Wickerhamomyces anomalus in Winemaking

Nowadays it is widely accepted that non-Saccharomyces yeasts, which prevail during the early stages of alcoholic fermentation, contribute significantly to the character and quality of the final wine. Among these yeasts, Wickerhamomyces anomalus (formerly Pichia anomala, Hansenula anomala, Candida pelliculosa) has gained considerable importance for the wine industry since it exhibits interesting and potentially exploitable physiological and metabolic characteristics, although its growth along fermentation can still be seen as an uncontrollable risk. This species is widespread in nature and has been isolated from different environments including grapes and wines. Its use together with Saccharomyces cerevisiae in mixed culture fermentations has been proposed to increase wine particular characteristics. Here, we review the ability of W. anomalus to produce enzymes and metabolites of oenological relevance and we discuss its potential as a biocontrol agent in winemaking. Finally, biotechnological applications of W. anomalus beyond wine fermentation are briefly described.