Potential production of 2-phenylethanol and 2-phenylethylacetate by non-Saccharomyces yeasts from Agave durangensis

Characterization of mating type on aroma production and metabolic properties wild Kluyveromyces marxianus yeasts

Kluyveromyces marxianus yeasts represent a valuable industry alternative due to their biotechnological potential to produce aromatic compounds. 2-phenylethanol and 2-phenylethylacetate are significant aromatic compounds widely used in food and cosmetics due to their pleasant odor. Natural obtention of these compounds increases their value, and because of this, bioprocesses such as de novo synthesis has become of great significance. However, the relationship between aromatic compound production and yeast's genetic diversity has yet to be studied. In the present study, the analysis of the genetic diversity in K. marxianus isolated from the natural fermentation of Agave duranguensis for Mezcal elaboration is presented. The results of strains in a haploid and diploid state added to the direct relationship between the mating type locus MAT with metabolic characteristics are studied. Growth rate, assimilate carbohydrates (glucose, lactose, and chicory inulin), and the production of aromatic compounds such as ethyl acetate, isoamyl acetate, isoamyl alcohol, 2-phenylethyl butyrate and phenylethyl propionate and the diversity in terms of the output of 2-phenylethanol and 2-phenylethylacetate by de novo synthesis were determinate, obtaining maximum concentrations of 51.30 and 60.39 mg/L by ITD0049 and ITD 0136 yeasts respectively.

Bioproduction of 2-Phenylethanol through Yeast Fermentation on Synthetic Media and on Agro-Industrial Waste and By-Products: A Review

Due to its pleasant rosy scent, the aromatic alcohol 2-phenylethanol (2-PE) has a huge market demand. Since this valuable compound is used in food, cosmetics and pharmaceuticals, consumers and safety regulations tend to prefer natural methods for its production rather than the synthetic ones. Natural 2-PE can be either produced through the extraction of essential oils from various flowers, including roses, hyacinths and jasmine, or through biotechnological routes. In fact, the rarity of natural 2-PE in flowers has led to the inability to satisfy the large market demand and to a high selling price. Hence, there is a need to develop a more efficient, economic, and environmentally friendly biotechnological approach as an alternative to the conventional industrial one. The most promising method is through microbial fermentation, particularly using yeasts. Numerous yeasts have the ability to produce 2-PE using l-Phe as precursor. Some agro-industrial waste and by-products have the particularity of a high nutritional value, making them suitable media for microbial growth, including the production of 2-PE through yeast fermentation. This review summarizes the biotechnological production of 2-PE through the fermentation of different yeasts on synthetic media and on various agro-industrial waste and by-products.

Nonconventional yeasts to produce aroma compounds by using agri-food waste materials

Nowadays, biotechnological applications are emphasized to ensure sustainable development by reutilizing waste materials to prevent ecological problems and to produce or recover compounds that may have positive effects on health. Yeasts are fascinating microorganisms that play a key role in several traditional and innovative processes. Although Saccharomyces is the most important genus of yeasts, and they are major producers of biotechnological products worldwide, a variety of other yeast genera and species than Saccharomyces that are called 'non-Saccharomyces' or 'nonconventional' yeasts also have important potential for use in biotechnological applications. Some of the nonconventional yeast strains offer a unique potential for biotechnological applications to produce valuable secondary metabolites due to their characteristics of surviving and growing in such extreme conditions, e.g. wide substrate range, rapid growth, thermotolerance, etc. In this review, we aimed to summarize potential biotechnological applications of some nonconventional yeasts (Kluyveromyces spp., Yarrowia spp., Pichia spp., Candida spp., etc.) to produce industrially important aroma compounds (phenylethyl alcohol, phenylethyl acetate, isobutyl acetate, diacetyl, etc.) by reutilizing agri-food waste materials in order to prevent ecological problems and to produce or recover compounds that may have positive effects on health.

Utilization of Agave durangensis leaves by Bacillus cereus 4N for polyhydroxybutyrate (PHB) biosynthesis

Lignocellulosic wastes may provide a means to economize polyhydroxybutyrate (PHB) production. This study has proposed the use of Agave durangensis leaves obtained from the artisanal mezcal industry as a novel substrate for this aim. Results revealed an increase in PHB biosynthesis (0.32 g/L) and improvement in %PHB (16.79-19.51%) by Bacillus cereus 4N when A. durangensis leaves used as carbon source were physically pre-treated by ultrasound for 30 min (ADL + US30') and thermally pre-treated (ADL + Q). Chemical analyses and SEM studies revealed compositional and morphological changes when A. durangensis leaves were physically pre-treated. Also, elemental analysis of growth media showed that carbon/nitrogen ratios of 14-21, and low nitrogen, hydrogen, and protein content were well-suited for PHB biosynthesis. Confocal microscopy revealed morphological changes in the bacterial cell and carbonosome structure under the influence of different substrates. Finally, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analyses showed that homopolymeric PHB with a high thermal-resistance (271.94-272.89 °C) was produced. Therefore, the present study demonstrates the potential use of physically pre-treated A. durangensis leaves to produce PHB. These results promote the development of a circular economy in Mexico, where lignocellulosic wastes can be employed to produce value-added biotechnological products.

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.