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1、ORIGINAL RESEARCHOpen Access Sustainable fermentation processing of two revalorized agro-industrial discards: carrot and brewers yeast Nora R Aimaretti1,2*, Adriana L Clementz1,2, Agustn Codevilla2, Mara L Rojas3and Juan C Yori1 Abstract An integrated and sustainable fermentation process was develop
2、ed which enabled both the revalorization of two regional agro-industrial discards as well as by-product reuse. Carrot and brewers yeast, which are commonly used for animal feed, were processed to obtain 77.5 L of ethanol, 450 kg of solid waste called bagasse, 970 L of liquid effluent called vinasse,
3、 and 39.8 kg CO2per each ton of discarded carrot. Results showed that the obtained bagasse was suitable for feeding 55 animals (calfs). The dilution of vinasse with fresh water (1:5) satisfied the requirements necessary to be used as beverage for the same number of animals, leaving a remnant which c
4、ould be newly diluted (1:5) and used to irrigate a 0.025-ha carrot crop, the land dimension required to grow 1 ton of carrot. Keywords: Discards, Carrot, Yeast, Fermentation, Ethanol, Sustainable Background First-generation biofuels, derived from agricultural prod- ucts (corn, sugarcane, palm oil, r
5、apeseed, or soybean), have produced an impact on grain prices, tightening the supply chain and the availability of land for food produc- tion 1. The transformation of forests, savannahs, or pastureland into farms for biofuel production could lead to greater CO2emission than the emission reduction th
6、ese biofuels could produce 2,3. Consequently, serious damages to the ecosystems have been produced. Second- generation bioethanol is a biofuel made from nonedible raw materials 4. Wastes or discards should no longer be seen as a burden but rather as another source of material such as energy fuel 1,5
7、. Thus, some organic waste may be incorporated as low-cost raw materials for second- generation bioethanol production, depending on the waste composition. Due to the wide variety of techno- logical alternatives for the production of ethanol through fermentation, a global analysis of the process is r
8、equired, leading to the development of a sustainable process, which cooperates with the final disposal of certain existing wastes in each region 6-9. A particular case of a fermentable substrate is the one represented by the discards of carrot (Daucus carota) cultivation. The cultivated area in Sant
9、a Fe (Argentina) is approximately 1,500 ha, and its average yield is nearly 40 tons (t) ha1. Only 65%to 90% of carrot harvest meets the quality standards; consequently, during harvest time, 20 to 100 t of carrots with an optimal degree of freshness and maturity are discarded daily due to a sizing pr
10、oblem and then directed to animal feed 10. Carrot is one of the most efficient crops in biomass accumulation 11, and it may be enzymatically hydrolyzed to increase yields 7. In general, plants accumulate carbohydrates, e.g., starch. However, carrot is one of the few plants that ac- cumulate free sug
11、ars into vacuoles (40% to 60% of total carbohydrates) as reserve carbohydrates. For free sugars, 95% is composed of sucrose, fructose, and glucose, which, together with terpenes, are the main determinants of carrot taste. Among the carbohydrates present in car- rots, reducing sugars (RS) (fructose a
12、nd glucose) are present in an equimolecular amount 12,13. In addition, in the same geographical area, 1 t of Saccharomyces cerevisiae yeast cells is discarded daily by a beer manu- facturing industry. So far, the elimination of these yeast * Correspondence: naimarettifbcb.unl.edu.ar 1Instituto de In
13、vestigaciones en Catlisis y Petroqumica, Facultad de Ingeniera Qumica, Universidad Nacional del Litoral, Santa Fe 3000, Argentina 2Laboratorio de Investigaciones Aplicadas, Facultad de Qumica, Universidad del Centro Educativo Latinoamericano, Av Pellegrini 1332, Rosario 2000, Argentina Full list of
14、author information is available at the end of the article 2013 Aimaretti et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http:/creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and re
15、production in any medium, provided the original work is properly cited. Aimaretti et al. International Journal of Energy and Environmental Engineering 2013, 4:24 http:/www.journal- cells has not been solved yet due to their elevated bio- chemical oxygen demand (BOD), and consequently, no process is
16、applied to reuse them 10. Taking into account the above considerations, the aims of this study are the following: (1) to develop a sustain- able process for production of second-generation ethanol from two regional agro-industrial discards: carrot as sub- strate and brewers yeast as biocatalyst, and (2) to qualita- tively and quantitatively evaluate the effluents generated by the process in order to propose solutions to make it sustaina
