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Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011molasses improved yeast yield, even in the absence of aeration. Historically speaking,Claudon and Vigreux appeared to have been the first to patent in 1882 a process describingthe use of molasses for growing yeast and in 1895 Elion proposed to use molasses enrichedwith phosphoric acid. The early twentieth century, large amounts of molasses becameavailable at minimal price for yeast manufacturing [Gelinas, 2010].In the last four years European Union registered a decline in sugar beet productionafter the limitation of exports by the World Trade Organization. [http://www.agroinfo.ro,2011]. As regards the sugar beet situation in Romania, in this moment the area cultivated isaround 20000 ha and it is sure that sugar beet will be considered in the next future as anenergy crop. The cultivated area has halved after Romanian accession (from 40,000hectares in 2006) when it was established in negotiations with the EU a quota of sugar forRomania [http://www.capital.ro, 2011]. Under these conditions, alcohol and yeast factoriesin Romania were forced to resort to imports of sugar cane molasses from countries such asBrazil.Currently applied production technologies for baking yeast provide continuousaccumulation of biomass. The main purpose of manufacturing technology of baking yeastis to obtain a quantity of high quality yeast biomass with minimum consumption of rawmaterials and utilities. The modern baking yeast manufacturing was established around1920. [Gelinas, 2010]Saccharomyces cerevisiae known as baking yeast can be considered one of themost cultivated microorganism, and has been used extensively for the production of singlecellprotein (SCP) used as food and feed. Baking yeast belongs to the speciesSaccharomyces cerevisiae, according to the classification of Hansen in 1904, and representsonly a yeast culture [Hansen, 1896]. Baking yeast is top fermenting yeast strain capable ofproducing fermentation of sugars in the dough with the formation of ethyl alcohol and CO 2 ,raising agents of dough, and other products, with a role in bread-making. One of the mostimportant requisites in the commercial production of baker’s yeast is rapid growth and highbiomass yield [Benitez et al., 1996].As regards the utilisation of adjuncts in order to increase technological yields, asearly as 1877 specific supplements for liquid media (such as nitrogen and vitamins) wereused. Starting with 1883, molasses supplementation with nitrogen sources as ammoniumsalts was proposed by Scard for promoting yeast growth at alcohol production, a practicethat would later be very important in modern yeast manufacturing [Gelinas, 2010].Nitrogen is normally supplied through the addition of ammonium salts, aqueous ammonia,or anhydrous ammonia [Chen and Chiger, 1985].Mineral requirements of molasses include nitrogen, potassium, phosphate,magnesium, and calcium. As regards potassium and calcium, molasses normally providessufficient quantities of these minerals. Phosphates and magnesium are added in the form ofphosphoric acid or phosphate salts and magnesium salts [Reed and Peppler, 1973]. Besidesthese, molasses needs iron, zinc, copper, manganese, and molybdenum are also required intrace amounts.The yeast growth process also requires several vitamins, such as biotin, inositol,pantothenic acid, and thiamine. In the absence of biotin baking yeast is not able to grow.Both cane and beet molasses usually provide enough inositol and pantothenic acid for yeastgrowth in order to obtain maximum yields of biomass. Beet molasses is deficient in biotin124
Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011and the variations of this factor explain in most of the times, in practice, variable yields ofyeast [Reed and Peppler, 1973; Assessment of VOC emissions, 1992; Manualul inginerului,2002; White, 1954].The present study is in line with other researches in order to provide the mostappropriate technological solutions as procedures to be applied in the industrialbiotechnological processes, such as food fermentation industries. The aim of this study wasto investigate the comparison in yeast biomass accumulation between culture media basedon sugar beet and sugar cane molasses, in order to propose the most suitable formulationunder specific conditions of decline of sugar industry in Romania.2. MATERIALS AND METHODSANALYTICAL METHODS• The soluble dry matter content in molasses was determined by AOAC Official Method932.14, using a double dilution of molasses;• The moisture content in molasses was determined by AOAC Official Method 966.20(Karl Fisher method);• The total sugar, initial reducing sugar and sucrose in molasses were determined by Luff-Schoorl method;• The protein content in pressed biomass was determined by Kjeldahl method, calculated asN x 6.25 (AOAC 920.53), using 0.5 g test portion (AOAC 962.10). Digestion wasperformed for 30 min after solution cleared. The protein was determined on cell biomassharvested at the end of the experiments;• The ash content in molasses was determined by AOAC Official Method 900.02(gravimetric method, using 5 g test portion). Result was expressed as percent ash and theash content was calculated by using the formula given below:Ash (g/l00g) = [(weight of dish with sample after calcination - weight of emptydish/weight of dish with sample before calcination - weight of empty dish) x 0.9] x1000.9 – coefficient for transformation of sulphated ash into conventional ash;• The solid content in yeast biomass was determined by AOAC Official Method 961.06(the method of 16 hours drying);• The yeast cell concentration was estimated by measuring spectrophotometrically in UV-Vis the optical density (OD) of the culture at 600 nm using a conversion factor of 0.50OD for 1 ×10 7 cells, and also by weighing the dried biomass samples on aluminiumdishes at 100°C for 24 h;• Life yeast cells (viability) were measured by methylene blue stain.EXPERIMENTAL ORGANISMS (MICRO-ORGANISMS AND INOCULUM)A pure culture of S. cerevisiae (ICA Collection of Microorganisms) was usedthroughout this work for the formation of yeast biomass. The yeast strains used in this workS. cerevisiae baking yeasts MY2011 previously isolated and selected in order to obtainbaking yeast biomass [Regodon et al., 1997].MAINTENANCE MEDIUM125
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