Effect of Vinasse Recycling on Effluent Reduction from Distilleries: Case of Metehara Distillery, Ethiopia

This study was conducted at the ethanol plant of Metehara sugar factory, at a laboratory scale, to assess the effect of recycling vinasse into the fermentation process on effluent reduction. Vinasse is an effluent produced from distilleries. The experimental design included vinasse concentrations at 4 dilution rates (0 (control), 20, 35, 50, and 65% of process water) with 2 replicates and 6 responses, as follows: ethanol yield, fermentation efficiency, residual sugar concentration, cell count, cell viability, and calcium oxide content. In this study, the actual operational parameters of the ethanol plant were maintained during the experiment. The result of the experiment indicates that, with up to 20% vinasse recycling, there was no influential impact on the ethanol yield, the fermentation efficiency, the residual sugar concentration, or the calcium oxide content, attributable to the recycling, as compared to the control. Above 20% vinasse recycling, ethanol yield and fermentation efficiency decreased sharply from those of the control. In addition, with 20% vinasse recycling put into practice, the amount of vinasse generated will be reduced by about 19.5% and about 114.2 tons of water will be saved per day. Moreover, the excess amount of vinasse produced by the distillery, which is beyond the handling capacity of bio-compost plant of the distillery, will reduce from 105 to 36.8 tons per day. Therefore, it is possible to recycle vinasse into the fermenter up to 20% on dilution water of Metehara distillery, without causing any impacts on the distillery’s performance.

Acetaldehyde metabolism in industrial strains of Saccharomyces cerevisiae inhibited by SO2 and cooling during alcoholic fermentation

Aim: The addition of SO2 is a common technique for stopping alcoholic fermentation by Saccharomyces cerevisiae and producing beverages with residual sugar. However, SO2 causes a metabolic shift in active yeast leading to the formation of acetaldehyde and resulting in higher preservative SO2 requirements in the final product. The current work investigated the effects of stopping alcoholic fermentation using two industrial strains of Saccharomyces cerevisiae, by means of cooling and/or addition of SO2, on the kinetics of hexoses and acetaldehyde.Methods and results: Alcoholic fermentation was conducted by inoculating natural Chardonnay grape must with two commonly used strains of Saccharomyces cerevisiae (CY3079 and EC1118). Ten days after inoculation, cooling (to 4 °C) and/or addition of SO2 (50-350 mg/L) were applied to stop fermentations at approximately 70-90 g/L of residual sugar. Incubations were carried out in an anaerobic chamber to prevent the formation of acetalhdeyde resulting from chemical oxidation. Samples were taken regularly and analysed for glucose, fructose and acetalhdyde levels.In this work, addition of SO2 to 150 mg/L or more were effective in inhibiting further and practically relevant degradation of hexoses even in non-cooled control treatments. With concurrent cooling, an addition to 50 mg/L was sufficient. Addition of SO2always led to a slow increase in yeast acetaldehyde formation over time, regardless of cooling or the apparent inhibition of yeast sugar metabolism. Acetaldehyde increases were reduced with larger SO2 additions.Conclusions: When using SO2 to stop alcoholic fermentations, large doses should be used and wines separated from the sedimented biomass soon thereafter. Nevertheless, rapid cooling remains preferable to SO2 addition and can prevent further microbial formation of acetaldehyde.Significance and impact of the study: Results from the current work show that acetaldehyde, and therefore bound SO2formation, can be reduced when alcoholic fermentation is halted to obtain wines with residual sweetness.

Acetaldehyde metabolism in industrial strains of Saccharomyces cerevisiae inhibited by SO2 and cooling during alcoholic fermentation

Aim: The addition of SO2 is a common technique for stopping alcoholic fermentation by Saccharomyces cerevisiae and producing beverages with residual sugar. However, SO2 causes a metabolic shift in active yeast leading to the formation of acetaldehyde and resulting in higher preservative SO2 requirements in the final product. The current work investigated the effects of stopping alcoholic fermentation using two industrial strains of Saccharomyces cerevisiae, by means of cooling and/or addition of SO2, on the kinetics of hexoses and acetaldehyde.Methods and results: Alcoholic fermentation was conducted by inoculating natural Chardonnay grape must with two commonly used strains of Saccharomyces cerevisiae (CY3079 and EC1118). Ten days after inoculation, cooling (to 4 °C) and/or addition of SO2 (50-350 mg/L) were applied to stop fermentations at approximately 70-90 g/L of residual sugar. Incubations were carried out in an anaerobic chamber to prevent the formation of acetalhdeyde resulting from chemical oxidation. Samples were taken regularly and analysed for glucose, fructose and acetalhdyde levels.In this work, addition of SO2 to 150 mg/L or more were effective in inhibiting further and practically relevant degradation of hexoses even in non-cooled control treatments. With concurrent cooling, an addition to 50 mg/L was sufficient. Addition of SO2always led to a slow increase in yeast acetaldehyde formation over time, regardless of cooling or the apparent inhibition of yeast sugar metabolism. Acetaldehyde increases were reduced with larger SO2 additions.Conclusions: When using SO2 to stop alcoholic fermentations, large doses should be used and wines separated from the sedimented biomass soon thereafter. Nevertheless, rapid cooling remains preferable to SO2 addition and can prevent further microbial formation of acetaldehyde.Significance and impact of the study: Results from the current work show that acetaldehyde, and therefore bound SO2formation, can be reduced when alcoholic fermentation is halted to obtain wines with residual sweetness.

Saccharomyces uvarum yeast isolate consumes acetic acid during fermentation of high sugar juice and juice with high starting volatile acidity

Aim: A Saccharomyces uvarum isolate was assessed for its ability to metabolize acetic acid present in juice and during the fermentation of partially dehydrated grapes. The impact on other yeast metabolites was also compared using an S. uvarum isolate and an S. cerevisiae wine yeast. The upper limit of fruit concentration that allowed the S. uvarum isolate to ferment wines to < 5 g/L residual sugar was defined.Methods and results: Cabernet franc grapes were partially dehydrated to three different post-harvest sugar targets (24.5 °Brix, 26.0 °Brix, and 27.5 °Brix) along with non-dehydrated grapes (21.5 °Brix control). Musts from all treatments were vinified with either the S. uvarum isolate CN1, formerly identified as S. bayanus, or S. cerevisiae EC1118. All wines were successfully vinified to less than 5 g/L residual sugar. Fermentation kinetics between the two yeasts were similar for all wines other than 27.5 °Brix, where CN1 took three days longer. During fermentation with CN1, acetic acid peaked on day two, then decreased in concentration, resulting in final wine acetic acid lower than that measured on day two. Wines fermented with EC1118 showed an increase in acetic acid over the time-course of fermentation. Significantly lower wine oxidative compounds (acetic acid, acetaldehyde and ethyl acetate) and higher glycerol resulted in wine produced with CN1 in comparison to EC1118. Both yeasts produced comparable ethanol at each Brix level tested. Further studies showed that CN1 lowered acetic acid seven-fold from 0.48 g/L in juice to 0.07 g/L in wine whereas EC1118 reduced acetic acid to 0.18 g/L.Conclusions: The autochthonous S. uvarum yeast isolate successfully fermented partially dehydrated grapes to < 5 g/L sugar up to 27.5 ºBrix. The consumption rate of acetic acid was faster than its production during fermentation, resulting in low acetic acid, acetaldehyde and ethyl acetate in wine in comparison to a commercial S. cerevisiae yeast while consistently producing higher glycerol.Significance and impact of the study: The S. uvarum yeast isolate can metabolize acetic acid during fermentation to significantly lower acetic acid, ethyl acetate and acetaldehyde in wine. It can also reduce acetic acid by seven-fold from the starting juice to the finished wine, which could have potential application for managing sour rot arising in the vineyard or during the dehydration process in making appassimento-style wines.

Electrophysiological responses to sugars and amino acids in the nucleus of the solitary tract of type 1 taste receptor double-knockout mice

Strong evidence supports a major role for heterodimers of the type 1 taste receptor (T1R) family in the taste transduction of sugars (T1R2+T1R3) and amino acids (T1R1+T1R3), but there are also neural and behavioral data supporting T1R-independent mechanisms. Most neural evidence for alternate mechanisms comes from whole nerve recordings in mice with deletion of a single T1R family member, limiting conclusions about the functional significance and T1R independence of the remaining responses. To clarify these issues, we recorded single-unit taste responses from the nucleus of the solitary tract in T1R double-knockout (double-KO) mice lacking functional T1R1+T1R3 [KO1+3] or T1R2+T1R3 [KO2+3] receptors and their wild-type background strains [WT; C57BL/6J (B6), 129X1/SvJ (S129)]. In both double-KO strains, responses to sugars and a moderate concentration of an monosodium glutamate + amiloride + inosine 5′-monophosphate cocktail (0.1 M, i.e., umami) were profoundly depressed, whereas a panel of 0.6 M amino acids were mostly unaffected. Strikingly, in contrast to WT mice, no double-KO neurons responded selectively to sugars and umami, precluding segregation of this group of stimuli from those representing other taste qualities in a multidimensional scaling analysis. Nevertheless, residual sugar responses, mainly elicited by monosaccharides, persisted as small “sideband” responses in double-KOs. Thus other receptors may convey limited information about sugars to the central nervous system, but T1Rs appear critical for coding the distinct perceptual features of sugar and umami stimuli. The persistence of amino acid responses supports previous proposals of alternate receptors, but because these stimuli affected multiple neuron types, further investigations are necessary. NEW & NOTEWORTHY The type 1 taste receptor (T1R) family is crucial for transducing sugars and amino acids, but there is evidence for T1R-independent mechanisms. In this study, single-unit recordings from the nucleus of the solitary tract in T1R double-knockout mice lacking T1R1+T1R3 or T1R2+T1R3 receptors revealed greatly reduced umami synergism and sugar responses. Nevertheless, residual sugar responses persisted, mainly elicited by monosaccharides and evident as “sidebands” in neurons activated more vigorously by other qualities.

Residual sugar from microalgae biomass harvested from phycoremediation of swine wastewater digestate

The present study assessed the carbohydrate and sugar production from Chlorella spp. biomass harvested from a field scale reactor simulating phycoremediation of swine wastewater. The microalgae biomass was mainly composed by (%): carbohydrates (41 ± 0.4), proteins (50 ± 0.4), and lipids (1.3 ± 0.5). The residual sugar present in the biomass was extracted via acid hydrolysis. Among different concentrations of sulfuric acid tested (i.e., 47, 94, 188, 281 and 563 mM), significantly higher sugar content was obtained with 188 mM (0.496 g-sugar g−1 microalgae-DW). The concentration of sugar present in the microalgae did not differ significantly between the biomasses harvested by either centrifugation or coagulation-flocculation. Two commercially available strains of yeast (i.e., Saccharomyces cerevisiae and S. cerevisiae chardonnay) were tested for their capability to ferment sugar from lyophilized microalgae biomass. S. cerevisiae chardonnay showed a significantly faster consumption of sugar during the exponential growth phase. Both strains of yeast were capable of consuming most of the sugar added ≅ 8 g L−1 within 24 h. Overall, the results suggest that carbohydrate-rich microalgae biomass obtained from the phycoremediation of swine wastewaters can play an important role in green design for industries seeking alternative sources of feedstock rich in sugar.

Cooperative valorization of lignin and residual sugar to polyhydroxyalkanoate (PHA) for enhanced yield and carbon utilization in biorefineries

Cooperative valorization of lignin and residual sugar has the potential to improve the sustainability and profitability of biorefineries.

APPLICATION OF SENSORY ANALYSES IN THE DEVELOPMENT OF A NEW APPLE CIDER

The development of a sparkling apple cider based on French technology and quality and desirable characteristics for Brazilian consumer may be a stratagem to development of a new beverage. The objective of this work was to develop and to characterize this beverage through physical-chemical and sensory analysis. The ordering and acceptability test and quantitative descriptive analysis (QDA) were performed in this work. The QDA was performed with 13 selected and trained testers. 16 aspects of product were evaluated: color, foam, turbidity, brightness, bubbles, the fruity, alcoholic, acetic, and fermented aromas, sweetness, astringency, acidity, alcohol, apple flavor and viscosity. The alcoholic degree was standardized in 4.5 oGL. The ordering test showed 50.0 g L-1 and 0.75 g 100mL-1 of residual sugar and acidity, respectively. The foam characteristics were obtained with 4.0 g hL-1 of propylene glycol alginate. The residual sugar was standardized with cryoconcentrated apple juice, which provided striking fruity aroma. The product was classified as sweet, low viscosity, cloudy however yellow as beer, with pleasant and persistent foam and bubbles. The acceptance rate was 81.6%, with purchase intent of circa 85.0%. The results indicate a high quality sparkling beverage with good marketing perspectives.