Flavor mystery of Chinese traditional fermented baijiu: The great contribution of ester compounds.

Flavor mystery of Chinese traditional fermented baijiu: The great contribution of ester compounds

Microalgae biomass has garnered significant attention as a renewable energy feedstock and alternative to petroleum-based fuels. The diverse metabolism of green microalgae species additionally provides opportunities for recovery of products for feed, food, nutraceutical, cosmetic, and biopharmaceutical industries. Recently, the concept of using microalgae as part of a biorefinery model has been adopted in place of refinery methods focused on recovering one target product. This has led to producers exploring co-production of high value and high volume products in an effort to improve process economics. With numerous potential products and applications, the biomass source or specific strain must be carefully selected to accumulate extractable levels of the target molecule(s). It is additionally imperative to understand the morphology and metabolism of the selected strain to cost-effectively manage all stages of commercial production. This review will focus specifically on microalgae in the division of Chlorophyta, or green algae and their extracellular matrices (ECM), potential for commercial products, and finally describe a holistic approach for biomolecule extraction and recovery. Additionally, cell disruption and fractionation methods for recovery of biomolecules for commercial products are highlighted along with an alternative method, aqueous enzymatic processing for multiple biomolecule extraction and recovery from green microalgae. An emphasis is placed on connecting the morphological characteristics of microalgae ECM or organelle membranes to implications on separation and purification technologies.

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Green microalgae biomolecule separations and recovery

The employment of multi-species starter cultures has growing importance in modern winemaking for improving the complexity and wine attributes. The assessment of compatibility for selected species/strains at the industrial-scale is crucial to assure the quality and the safety associated with fermentations. An aspect particularly relevant when the species belong to non-Saccharomyces, Saccharomyces spp. and malolactic bacteria, three categories with different biological characteristics and oenological significance. To the best of our knowledge, the present report is the first study regarding the utilization of a combined starter culture composed of three strains of non-Saccharomyces, Saccharomyces cerevisiae and Lactobacillus plantarum for production of wine at the industrial scale. More in-depth, this work investigated the oenological potential of the autochthonous characterized strains from the Apulian region (Southern Italy), Candida zemplinina (syn. Starmerella bacillaris) 35NC1, S. cerevisiae (NP103), and L. plantarum (LP44), in co-inoculation following a complete scale-up scheme. Microbial dynamics, fermentative profiles and production of volatile secondary compounds were assessed in lab-scale micro-vinification tests and then the performances of the mixed starter formulation were further evaluated by pilot-scale wine production. The above results were finally validated by performing an industrial-scale vinification on 100HL of Negroamaro cultivar grape must. The multi-starter formulation was able to rule the different stages of the fermentation processes effectively, and the different microbial combinations enhanced the organoleptic wine features to different extents. The findings indicated that the simultaneous inoculation of the three species affect the quality and quantity of several volatile compounds, confirming that the complexity of the wine can reflect the complexity of the starter cultures. Moreover, the results underlined that the same mixed culture could differently influence wine quality when tested at the lab-, pilot- and industrial-scale. Finally, we highlighted the significance of employment non-Saccharomyces and L. plantarum, together with S. cerevisiae, autochthonous strains in the design of custom-made starter culture formulation for typical regional wine production with pronounced unique quality.

https://www.mdpi.com/2076-2607/8/5/726/pdf

Effect of Co-Inoculation of Candida zemplinina, Saccharomyces cerevisiae and Lactobacillus plantarum for the Industrial Production of Negroamaro Wine in Apulia (Southern Italy).

The objective of this study was to determine the efficiency of rye and barley starch hydrolysis in mashing processes using cereal malts as a source of amylolytic enzymes and starch, and to establish the volatile profile of the obtained agricultural distillates. In addition, the effects of the pretreatment method of unmalted cereal grains on the physicochemical composition of the prepared mashes, fermentation results, and the composition of the obtained distillates were investigated. The raw materials used were unmalted rye and barley grains, as well as the corresponding malts. All experiments were first performed on a semi-technical scale, and then verified under industrial conditions in a Polish distillery. The fermentable sugars present in sweet mashes mostly consisted of maltose, followed by glucose and maltotriose. Pressure-thermal treatment of unmalted cereals, and especially rye grains, resulted in higher ethanol content in mashes in comparison with samples subjected to pressureless liberation of starch. All agricultural distillates originating from mashes containing rye and barley grains and the corresponding malts were characterized by low concentrations of undesirable compounds, such as acetaldehyde and methanol. The distillates obtained under industrial conditions contained lower concentrations of higher alcohols (apart from 1-propanol) than those obtained on a semi-technical scale.

https://www.mdpi.com/1420-3049/21/10/1320/pdf

Fermentation Results and Chemical Composition of Agricultural Distillates Obtained from Rye and Barley Grains and the Corresponding Malts as a Source of Amylolytic Enzymes and Starch

The formation of volatile by-products during alcoholic fermentation is affected by many factors such as the type of yeast strain applied, technological parameters of the process and the raw material used as the main constituent of the fermentation medium. The influence of availability of sugars released by the plant polysaccharide hydrolysis on the concentration of higher alcohols during the fermentation process was analyzed. Significant differences in the starch hydrolysis dynamics for various raw materials, entailing changes in availability of sugars such as glucose, maltose, maltotriose and maltotetraose, are reported. The highest glucose concentration after the mashing process (93.8 ± 3.8 mg cm−3) was observed for the maize mash (as compared to that of the rye and amaranth mashes, 24.9 ± 0.9 and 46.9 ± 2.5 mg cm−3, respectively). The highest glucose content in the maize mash resulted in a significantly higher isobutanol and 2-methyl-1-butanol content at the initial stage of fermentation, irrespective of the yeast strain used (D-2 or As-4). The highest final total content of fusel alcohols (ca. 5,460 mg dm−3 EtOH, on average) was also found in the distillates produced from the maize mash. However, the concentration of higher alcohols in the rye and amaranth distillates was similar and reached the level of ca. 3,440 mg dm−3 EtOH, on average. It is shown that the polysaccharide hydrolysis rate, and hence the rate at which fermenting sugars are released, significantly affects the concentration of higher alcohols in the produced distillates.

Influence of various yeast strains and selected starchy raw materials on production of higher alcohols during the alcoholic fermentation process

A semi-quantitative method (the enzymatic activity index, EI) and a quantitative method (the amount of reducing sugars, RS) have been used for selecting cellulolytic microorganisms. The analysis was performed with 90 isolates of filamentous fungi selected from pulp mill materials. In both methods 1% low viscosity carboxymethylcellulose (1% CMC l.v.) was used as a substrate. For n = 90, no correlation between the parameters has been found. A further analysis was carried out for 12 selected isolates: 6 with the highest RS values and 6 with the highest EI values. For the chosen fungi, also cultivated on 1% CMC l.v. medium, the following parameters have been determined: the total cellulase activity (filter paper assay, FPase), endoglucanase (CMCase) activity, β -glucosidase (CBase) activity, and the changes in the culture medium viscosity (DV). The statistical analysis revealed a negative, moderately marked correlation between EI and RS and clearly marked positive correlations for two pairs: RS-FPase and DV-FPase. A high positive correlation between RS and DV has also been observed. Correlations between EI, RS, DV, CMCase, and CBase activities were weak. It was shown that the quantitative parameter RS is more suitable than EI for the evaluation of the total cellulolytic activity of filamentous fungi. The application of CMC as the only source of carbon in the culture media and the subsequent determination of EI or RS has failed to provide the means for selecting fungi with a high endoglucanase (CMCase) activity.

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Beata Miklaszewska

Papers

Influence of various yeast strains and selected starchy raw materials on production of higher alcohols during the alcoholic fermentation process

Application of semi-quantitative and quantitative methods for the selection of cellulolytic filamentous fungi isolated from pulp mill materials