Calculation of the Yield of an Alcoholic Fermentation

This study is associated with a result of an industrial process in the measurement of fermentative efficiency using physico-chemical data obtained routinely in the laboratory. In Brazil, besides sugar, final molasses, which is a by-product of sugar production, is also used in the production of ethanol. The alcohol is obtained after the fermentation of the broth or a mixture of molasses and broth, which consists of a biochemical process. Before being sent to fermentation the broth should be purified. The results obtained in the laboratory showed that the fermentation presented a yield of 91.55% (CTC Method) and 91.39% (Fermentec Method), close yields from 86.3 to 93.4% quantified in two harvests (2010 and 2011) operating in batch fed as in the current work. Keywords— alcohol, fermentation, sugar and ethanol industry, ethanol methodology, fermentative yield.


I. INTRODUCTION
According to Lima et al., (2001), alcoholic fermentation has three main phases: preliminary phase, tumultuous and final or complementary phase. In the industrial operation, in the fermentation, yields from 86.3 to 93.4 were quantified in two harvests "2010 and 2011" Andrietta et al., (2012) operating in batch fed as in the current work. Silva et al., (2017) report that in the 2014/2015 harvest in industrial processing, fermentation efficiency of 89.99% was obtained; in the 2015/2016 crop, 92.04% were obtained. This shows that the fermentative efficiency varies between different harvests. The importance of this study is the use of experimental industrial results obtained in the sugarcane harvest of 2017, and uses them in the quantification of the fermentative yield, as carried out in the industry. The objective of this work is to show the results of the experiment performed in the laboratory of sugar and ethanol plant, in 24 hours of operation, comparing the methods of CTC (2005) and Fermentec, Silva et al., (2003) in the evaluation of the yield of alcoholic fermentation.

II. METHODOLOGY
The methodology used in this study consists of the use of experimental data of an industrial process in operation, using them to obtain the fermentative yield of the process described below. The must to ferment must have the concentration between 19 and 23° Brix; thus, the mixed broth is standardized with the addition of residual molasses from the manufacture of sugar or syrup from the evaporators. Yeasts produce a set of enzymes that catalyze the fermentation reaction with conversion of the sugars into ethanol. The formation of other compounds occurs during fermentation, such as glycerin, succinic acid, amyl, isoamyl, butyl and other alcohols. In the alcoholic fermentation in Brazil, the use of the discontinuous Melle-Boinot system is common. The yeasts are reused after separation by centrifugation of the fermented must in two fractions. Yeasts are sent to an acid treatment tank for reuse. The reuse of yeasts in subsequent fermentations minimizes cell multiplication. Thus, the sugar consumed converts to ethanol. The centrifuged wine is stored in a flywheel and is then distilled. The physico-chemical methods used in the industry where the present study ware carried out was described in (Silva et al., 2003). Industry software uses the equations described in the document. The efficiency of the alcoholic fermentation ware obtained under the determination of the ethanol produced as a function of th e Mass of Total Reducer Sugar, fed daily in the fermentation process or Residual Reducing Sugar of the dorna, with the practical equations used in the industry: "CTC" and "Fermentec".
After carrying out the primary sieving treatment, calcium hydroxide is added to the broth, following heating and subsequent decantation, treatment similar to that used in the manufacture of sugar. The cooling of the broth is carried out in two stages: in a heat exchanger (regenerative) operating countercurrent with the cold mixed broth, the broth being cooled to about 60°C; final cooling to approximately 30°C, in plate changer with water flowing in countercurrent (COPERSUCAR, 2010). The fermentation, where the conversion of the sugars into Invertase and zymase are the enzymes produced by yeast. Formation of other compounds occurs during fermentation, such as glycerin, succinic acid, amyl, isoamyl, butyl, and other alcohols. In the alcoholic fermentation in Brazil, it is common to use the Melle-Boinot discontinuous system. Yeasts are reused after separation by centrifugation of the fermented must in two fractions: yeast milk and wine as shown in Figure 1. Using practical equations of CTC (2005), the experimental results allow to quantify fermentation yield and other parameters, such as yeast loss (kf); produced glycerol (kg); losses of total sugars (kart); acidity (kac), fermentative yield (RF).   /dx.doi.org/10.22161/ijaers.6.6.62  ISSN: 2349-6495(P) | 2456-1908(O

III. RESULTS AND DISCUSSIONS
With the physicochemical analyzes performed in the laboratory to monitor the entire industrial process, the industrial results shown in Table 1 are reached.
The two calculation methods "CTC and FERMENTEC" presented similar results. Therefore, both methods are suitable for quantifying the fermentative yield. In addition, the results were close to the upper limit of the range reported in the literature: 86.3 to 93.4% (Andrietta et al., 2012).
The final fermentative yield of the CTC and Fermentec Methods were 91.55% and 91.39%, respectively. These results are used in the manufacture of ethanol, in process control, when fermentative efficiency is reduced.

IV. CONCLUSION
With the results of the analyzes presented in Table 1, used in the previous equations, the fermentation presented a yield of 91.55% (CTC Method) and 91.39% (Fermentec Method), close to the higher values obtained in ethanol plant in Brazil, which is 86,3 to 93,4%. The result shows the importance of obtaining data from the units with the physicochemical analyzes to obtain the efficiency of the process.