Lactic Acid Bacteria and Yeasts in Spontaneously Fermented Sorghum Sourdough

Motunrayo O. Ewuoso^1, , Oluwatoyin H. Animashaun² and Adedapo A. Adejumo³

¹Department of Science Laboratory Technology, Moshood Abiola Polytechnic, Abeokuta

²Department of Food Technology, Moshood Abiola Polytechnic, Abeokuta

³Departments of Public Health, Kwara State University, Malete

Cite this paper:
Motunrayo O. Ewuoso, Oluwatoyin H. Animashaun and Adedapo A. Adejumo. Lactic Acid Bacteria and Yeasts in Spontaneously Fermented Sorghum Sourdough. American Journal of Microbiological Research. 2020; 8(2):63-72. doi: 10.12691/ajmr-8-2-4

Abstract

Introduction: Generally, natural fermentations are carried out by yeast and lactic acid bacteria forming a complex microbiota that acts in cooperation. Yeast have a prominent role in the production of beverages, due to the ability to accumulate high levels of ethanol and to produce highly desirable aroma compounds, but lactic acid bacteria are particularly important in fermentation because they produce desirable acids, flavor compounds, and peptides that inhibit the growth of undesirable organisms [1]. Studies on the ecology of sourdough microflora may help in the understanding of the microbial dynamics and differences between groups of closely related microbial population in cereal (sourdough) fermentations. In most natural fermentation, starters used are poorly known [2]. Methodology: Lactic acid bacteria and yeasts were isolated from Sourdoughsusing pour plating methods as described by Harrigan and McCance [3]. Mann Rogosa Sharpe (MRS) and potato dextrose medium were used for culturing lactic acid bacteria and yeasts respectively. Cultured MRS plates were incubated anaerobically at 30°C for 48h while that of PDA plates were incubated in an incubator at 25°C for 72h. The microbial populations of the sourdoughs were enumerated on each day of fermentation. Isolation and sub-culturing was done until pure cultures were obtained. Result: The spontaneously fermentative lactic acid bacteria and yeast populating the fermenting sorghum sourdough observed in this study increased rapidly as the fermentation time increased. The mutual or synergistic relationship between the duo confirmed and justified Wood (2004) report in fermenting food matrix. Wood and Hodge (1985), describe the co-existence of lactic acid bacteria and yeast in food processing as very crucial. Conclusion: The microbiological and physicochemical analysis of sorghum sourdough fermented spontaneously showed a synergistic relationship of lactic acid bacterial and yeast growing in it. The titratable acidity, pH, and temperature of the fermenting sorghum sourdough increased with increase days of fermentation with higher values observed in sorghum vulgare.

Keywords:
sorghum sourdough fermentation yeast

This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

References:

[1]	Faria-Oliveira, F., Diniz, R.H.S., Godoy-Santos, F., Piló, F.B., Mezadri H., Castro, I.M. and Brandão, R.L. (2015). The role of yeast and lactic acid bacteria in the production of fermented beverages in South America. Agricultural and Biological Sciences. "Food Production and Industry", book edited by Ayman Hafiz Amer Eissa, ISBN 978-953-51- 2191-6.
[2]	Akinola, S.A. and Osundahunsi, O.F. (2017). Lactic acid bacteria and yeast diversities in spontaneously fermented millet sourdoughs. J Microbiol Biotech Food Sci. 6(4):1030-1035.
[3]	Harrigan W. F. andMccane M. F. (1976). Laboratory Methods in Food and Dairy Microbiology. Revised Edition. 452 S., 24 Abb. Academic Press. London-New York, San Francisco.
[4]	Das, M. ; Ganguly, A. ; Haldar, P., 2012. Effect of food plants on nutritional ecology of two acridids (Orthoptera: Acrididae) to provide alternative protein supplement for poultry. Turkish J. Zool., 36 (5): 699-718.
[5]	K. Jeyaram , W. Mohendro Singh, Angela Capece , Patrizia Romano. Molecular identification of yeast species associated with ‘Hamei’ — A traditional starter used for rice wine production in Manipur, India. International Journal of Food Microbiology 124 (2008) 115-125
[6]	Hansen J, et al. (2002). The level of MXR1 gene expression in brewing yeast during beer fermentation is a major determinant for the concentration of dimethyl sulfide in beer. FEMS Yeast Res 2(2):137-49
[7]	Das, M.; Ganguly, A.; Haldar, P., 2012. Annual biomass production of two acridids (Orthoptera: Acrididae) as alternative food for poultry. Spanish J. Agric. Res., 10 (3): 671-680
[8]	Aplevicz, K.S., Mazo, J.Z., Ilha, E.C., Dinon, A.Z. and Sant´Anna, E.S. (2014). Isolation and characterization of lactic acid bacteria and yeasts from the Brazilian grape sourdough. Braz. J. Pharm. Sci. 50(2): 1-8.
[9]	De Vuyst, L. and Neysens, P. (2005). The sourdough microflora: biodiversity and metabolic interactions, Trends in Food Science & Technology 16:43-56.
[10]	Arendt, E.K., Ryan, L.A.M. and Dal, B. F. (2007). Impact of sourdough on the texture of bread. Food Microbiol. 24:165-174.
[11]	Corsetti, A., Settani, L. and Van Sinderen, D. (2004). Characterization of bacteriocin-like inhibitory substances (BLIS) from sourdough lactic acid bacteria and evaluation of their in vitro and in situ activity. J. ApplMicrobiol. 96: 521-536.
[12]	De Vuyst, L., Schrijvers, V., Paramithiotis, S., Hoste, B., Vancanneyt, M. and Swings, J. (2002). The biodiversity of lactic acid bacteria in Greek traditional wheat sourdoughs is reflected in both composition and metabolite formation. Applied and Environmental Microbiology, 68: 6059-6069.
[13]	Valcheva, R., Ferchichi, M., Korakli, M., Ivanova, I., Gänzle, M. G. and Vogel, R. F. (2006). Lactobacillus nantensissp. nov. isolated from French wheat sourdough. International Journal of Systematic and Evolutionary Microbiology. 56: 587-591.
[14]	Edema, M.O. (2011). A Modified Sourdough Procedure for Non-Wheat Bread from Maize Meal. Food Bioprocess Technology. 4: 1264-1272.
[15]	Holzapfel, W.H. (2002). Appropriate starter culture technologies for small-scale fermentation in developing countries. International Journal of Food Microbiology. 75: 197-212.
[16]	Vogel, R.F., Müller, M., Stolz, P. and Ehrmann, M. (1996). Ecology in sourdoughs produced by traditional and modern technologies. Advances in Food Science 18(5-6): 152-159.
[17]	Steinkraus, K. H. (1996). Handbook of indigenous fermented foods. 2nd Ed., Marcel Dekker, New York 792 pp. ISBN 0824793528.
[18]	Steinkraus, K.H. (1997). Classification of fermented foods: worldwide review of household fermentation techniques. Food Control 8: 311-317.
[19]	Holzapfel, W.H., Haberer, P., Snel, J., Schillinger, U. and Huis In’t Veld, J.H.J. (1998). Overview of gut flora and probiotics. International Journal Food Microbiology. 41: 85-101.
[20]	Lee, C.H. (1997). Lactic acid fermented foods and their benefits in Asia. Food Control. 8: 259- 269.
[21]	Oyewole, O.B. (1997). Lactic fermented foods in Africa and their benefits. Food Control. 8: 289-297.
[22]	De Angelis, M., Di Cagno, R., Gallo, G., Curci, M., Siragusa, S., Crecchio, C., Parente, E. and Gobbetti, M. (2007). Molecular and functional characterization of Lactobacillus sanfrancisiences strains isolated from sourdough. International Journal of Food Microbiology 114(1): 69-82.
[23]	Saeed, M., Anjum, F.M., Zahoor, T., Nawaz, H. and Rehman, S.U. (2009). Isolation and characterization of starter culture from spontaneous fermentation of sourdough. Int. J. Agric. Biol. 11: 329-332.
[24]	Tortora, G.J., Funke, B.R. and Case, C.L. (2010). "5". Microbiology An Introduction (10 ed.). San Francisco, CA 94111, USA: Pearson Benjamin Cummings. p. 135.
[25]	Hui, Y.H., Meunier-Goddik, L., Josephsen, J., Nip, W.K. and Stanfield, P.S. (2004). Handbook of Food and Beverage Fermentation Technology. CRC Press. pp. 27 and passim.
[26]	Steinkraus, K.H. ed. (1995). Handbook of Indigenous Fermented Foods. Marcel Dekker.
[27]	Oguntoyinbo, F. A., Sanni, A. I. S., Franz, C. M. A. P. and Holzapfel, W. H. (2007). In vitro fermentation studies for selection and evaluation of Bacillus strains as starter cultures for the production of okpehe, a traditional African fermented condiment. Int. J. Food Microbiol. 113: 208-218.
[28]	Tamang, J. P. (2010b). Diversity of fermented foods. In:Tamang JP, Kailasapathy K., editors. (Eds.) Fermented Foods and Beverages of the World, CRC Press, Taylor and Francis Group, New York, 41-84.
[29]	Tamang, J. P. (2015a). Health Benefits of Fermented Foods and Beverages. New York, NY: CRC Press, Taylor and Francis; Group
[30]	Nout, M. J. R. and Aidoo, K. E. (2002). Asian fungal fermented food.In: The Mycota, ed Osiewacz H. D., editor. (New York, NY: Springer-Verlag), 23-47.
[31]	Tamang, J. P. (2010c). Diversity of fermented beverages. In: Fermented Foods and Beverages of the World, eds Tamang J. P., Kailasapathy K., editors. (New York, NY: CRC Press, Taylor and Francis Group) 85-125.
[32]	Wood, B.J.B. (1997). Microbiology of Fermented Foods. Blackie Academic and Professional, London.
[33]	Tou, E. H., Mouquet-River, C., Rochette, I., Traoré, A. S., Treche, S. and Guyot, J. P. (2007). Effect of different process combinations on the fermentation kinetics, microflora and energy density of ben-saalga, a fermented gruel from Burkina Faso. Food Chem. 100: 935-943.
[34]	Brandt, M. J. (2007). Sourdough products for convenient use in baking. Food Microbiol. 24:161-164.
[35]	De Vuyst, L., Vrancken, G., Ravyts, F., Rimaux, T. and Weckx S. (2009). Biodiversity, ecological determinants, and metabolic exploitation of sourdough microbiota. Food Microbiol. 26: 666-675.
[36]	Corsetti, A. and Settanni, L. (2007). Lactobacilli in sourdough fermentation. Food Res. Int. 40: 539-558.
[37]	Guyot, J. P. (2010). Fermented cereal products. In: Fermented Foods and Beverages of the World, edsTamang J. P., Kailasapathy K., editors. (New York, NY: CRC Press, Taylor and Francis Group) 247-261.
[38]	Moroni, A. V., Arendt, E. K., Bello, F. D. (2011). Biodiversity of lactic acid bacteria and yeasts in spontaneously-fermented buckwheat and teff sourdoughs. Food Microbiol. 28: 497-502.
[39]	Hammes, W.P., Brandt, M.J., Francis, K.L., Rosenheim, J., Seitter, M.F.H. and Vogelmann, S.A. (2005). Microbial ecology of cereal fermentations. Trends Food Sci. Technol. 16: 4-11.
[40]	Weckx, S., Meulen V., Maes, R., Scheirlinck, D., Huys, I., Vandamme, G.P. and De Vuyst, L. (2010). Lactic acid bacteria community dynamics and metabolite production of rye sourdough fermentations share characteristics of wheat and spelt sourdough fermentations. Food Microbiol. 27: 1000-1008.
[41]	Johnson, E. A. and Echavarri-Erasun, C. (2011). Yeast Biotechnology, in The Yeasts: A Taxonomic Study 5th Edn., Vol. 1, eds Kurtzman C., Fell J. W., Boekhout T., editors. (Amsterdam: Elsevier) 23.
[42]	Stiles, M. E. and Holzapfel, W. H. (1997). Lactic acid bacteria of foods and their current taxonomy. Int. J. Food Microbiol. 36: 1-29.
[43]	Salminen, S., Wright, A. V. and Ouwehand, A. (2004). Lactic Acid Bacteria Microbiology and Functional Aspects, 3rd Edn., New York, NY: Marcel Dekker.
[44]	Axelsson L., Rud I., Naterstad K., Blom H., Renckens B., Boekhorst J. et al. (2012). Genome sequence of the naturally plasmid-free Lactobacillus plantarum strain NC8 (CCUG 61730). J. Bacteriol.194:2391-2392.
[45]	Holzapfel, W. H. and Wood, B. J. B. (2014). Lactic Acid Bacteria: Biodiversity and Taxonomy. New York, NY: Wiley-Blackwell, 632.
[46]	Parkouda, C., Nielsen, D. S., Azokpota, P., Ouoba, L. I. I., Amoa-Awua, W. K., Thorsen, L. et al. (2009). The microbiology of alkaline-fermentation of indigenous seeds used as food condiments in Africa and Asia. Critical Rev. Microbiol. 35: 139-156.
[47]	Tamang, J. P. (2015b). Naturally fermented ethnic soybean foods of India. J. Ethnic Foods. 2: 8-17.
[48]	Kiers, J. L., Van laeken, A. E. A., Rombouts, F. M., Nout, M. J. R. (2000). In vitro digestibility of Bacillus fermented soya bean. Int. J. Food Microbiol.60:163-169.
[49]	Kubo, Y., Rooney, A. P., Tsukakoshi, Y., Nakagawa, R., Hasegawa, H. and Kimura, K. (2011). Phylogenetic analysis of Bacillus subtilis Strains applicable to natto (fermented soybean) production. Appl. Environ. Microbiol. 77: 6463-6469.
[50]	Urushibata, Y., Tokuyama, S. and Tahara, Y. (2002). Characterization of the Bacillus subtilisyws C gene, involved in ⌊-polyglutamic acid production. J. Bacteriol.184:337-343.
[51]	Nishito, Y., Osana, Y., Hachiya, T., Popendorf, K., Toyoda, A., Fujiyama, A., et al. (2010). Whole genome assembly of a natto production strain Bacillus subtilis natto from very short read data. BMC Genomics. 11: 243.
[52]	Martín, B., Garriga, M., Hugas, M., Bover-Cid, S., Veciana-Noqués, M. T. and Aymerich, T. (2006). Molecular, technological and safety characterization of Gram-positive catalase- positive cocci from slightly fermented sausages. Int. J. Food Microbiol. 107: 148-158.
[53]	Coton, E., Desmonts, M.H., Leroy, S., Coton, M., Jamet, E., Christieans, S. et al. (2010). Biodiversity of coagulase-negative Staphylococci in French cheeses, dry fermented sausages, processing environments and clinical samples. Int. J. Food Microbiol. 137: 221-229. 10.1016/j.ijfoodmicro.2009.11.023
[54]	Bourdichon, F., Casaregola, S., Farrokh, C., Frisvad, J. C., Gerds, M. L., Hammes W. P. et al. (2012). Food fermentations: microorganisms with technological beneficial use. Int. J. Food Microbiol. 154:87-97.
[55]	Watanabe, K., Fujimoto, J., Sasamoto, M., Dugersuren, J., Tumursuh, T. and Demberel, S. (2008). Diversity of lactic acid bacteria and yeasts in airag and tarag, traditional fermented milk products from Mongolia. World J. Microbiol. Biotechnol. 24:1313-1325.
[56]	Tamang, J. P. and Fleet, G. H. (2009). Yeasts diversity in fermented foods and beverages. In: Yeasts Biotechnology: Diversity and Applications, edsSatyanarayana T., Kunze G., editors. (New York, NY: Springer) 169-198.
[57]	Lv, X.C., Huang, X.L., Zhang, W., Rao, P.F. and Ni, L. (2013). Yeast diversity of traditional alcohol fermentation starters for Hong Qu glutinous rice wine brewing, revealed by culture-dependent and culture-independent methods. Food Control. 34: 183-190.
[58]	Kejžar, A., Gobec, S., Plemenitaš, A. and Lenassi, M. (2013). Melanin is crucial for growth of the black yeast Hortaeawerneckii in its natural hypersaline environment. Fungal Biol. 117: 368-379.
[59]	Gadanho, M., Libkind, D., and Sampaio, J.P. (2006). Yeast diversity in the extreme acidic environments of the Iberian pyrite belt. Microbial Ecol. 52: 552-563.
[60]	Hashim, N., Bharudin, I., Nguong, D., Higa, S., Bakar, F., Nathan, S., Rabu, A., Kawahara, H., Illias, R., Najimudin, N., Mahadi, N. and Murad, A. (2013). Characterization of Afp1, an antifreeze protein from the psychrophilic yeast Glaciozymaantarctica PI12. Extremophiles. 17: 63-73.
[61]	Tsuji, M., Yokota, Y., Shimohara, K., Kudoh, S. and Hoshino, T. (2013). An application of wastewater treatment in a cold environment and stable lipase production of antarctic basidiomycetous yeast Mrakiablollopis. PLoS One. 8:e59376.
[62]	Faria-Oliveira, F., Puga, S. and Ferreira, C. (2013) Yeast: World's finest Chef. In: Muzzalupo I, editor. Food Industry. Rijeka: Intec. p.519-547.
[63]	Conceição, L.E.F.R., Saraiva, M.A.F., Diniz, R.H.S., Oliveira. J., Barbosa, G.D., Alvarez, F., da Mata Correa, L.F., Mezadri, H., Coutrim, M.X., Afonso, R.J., Lucas, C., Castro, I.M. and Brandão, R.L. (2015). Biotechnological potential of yeast isolates from cachaça: the Brazilian spirit. Journal of Industrial Microbiology and Biotechnology 42:237-246.
[64]	Steensels, J. and Verstrepen, K.J. (2014). Taming wild yeast: potential of conventional and nonconventional yeast in industrial fermentations. Ann Rev Microbiol. 68: 61-80.
[65]	Kongkiattikajorn, J. (2012). Production of amylase from Saccharomyces diastaticus sp. and hydrolysis of cassava pulps for alcohol production. J AgricSciTechnolB. 2: 909-918.
[66]	Rogosa, M. (1974). Gram positive asporogenous, rod-shaped bacteria. In: Bergey's Manual of Determinative Bacteriology, Buchanan, R.E. and N.E. Gibbons (Eds.). 8th Edn., Williams and Wilkins, Baltimore, pp: 576-593.
[67]	Collins, C.H. and Lyne, P.M. (1984). Microbiological Methods. 5th Edn., Butterworths, London, ISBN: 9780408709576, pp:448.
[68]	Jay, M.J. (1986). Modern Food Microbiology. 3rd Edn., Van Nostrand Reinhold Co., New York, USA.
[69]	Kandler, C. and Weiss, N. (1986). The Genus Lactobacillus. In: Bergey's Manual of Systematic Bacteriology, Sneath, P.H.A., N.S. Mair, M.E. Sharpe and J.G. Holt (Eds.). Academic Press, London, pp: 1209.
[70]	Schillinger, U. and Lucke, F.K. (1987). Identification of Lactobacilli from meat and meat product. Food Microbiol. 4: 199-208.
[71]	Priest, F.G. and Campbell, I. (1996). Brewing Microbiology. 2nd Edn., International Center for Brewing and Distilling, Chapman and Hall, UK., pp:134-156.
[72]	Boone, D.R., Castenholz, R.W., Garrity, G.M., Brenner, D.J., Krieg, N.R. and Staley, J.T. (2005). Bergey's Manual® of Systematic Bacteriology. Springer Science & Business Media
[73]	Liu, W., Pang, H., Zhang, H. and Cai, Y. (2014). Biodiversity of Lactic Acid Bacteria. In: Zhang, H., Cai, Y.editors. Lactic Acid Bacteria. Springer Netherlands; p.103-203.
[74]	Hoover, D.G. and Steenson, L.R. (2014). Bacteriocins of lactic acid bacteria. Academic Press.
[75]	Horvath, P, Coute-Monvoisin, A.C., Romero, D.A., Boyaval, P., Fremaux, C. and Barrangou, R. (2009). Comparative analysis of CRISPR loci in lactic acid bacteria genomes. Int J Food Microbiol. 131:62-70.
[76]	Klein, G., Pack, A., Bonaparte, C. and Reuter, G. (1998). Taxonomy and physiology of probiotic lactic acid bacteria. Int J Food Microbiol. 41: 103-125.
[77]	Giraffa, G., Chanishvili, N. and Widyastuti, Y. (2010). Importance of Lactobacilli in food and feed biotechnology. Res Microbiol. 161: 480-487.
[78]	König, H. and Fröhlich, J. (2009). Lactic acid bacteria. In: Biology of Microorganisms on Grapes, in Must and in Wine. Springer. p.3-29.
[79]	Ananou, S., Maqueda, M., Martínez-Bueno, M. and Valdivia, E. (2007). Biopreservation, an ecological approach to improve the safety and shelf-life of foods. In: Communicating Current Research and Educational Topics and Trends in Applied Microbiology. Formatex. 475-486.
[80]	Howarth, G.S. and Wang, H. (2013). Role of endogenous microbiota, probiotics and their biological products in human health. Nutrients. 5: 58-81.
[81]	Asmahan, A. A. (2010). Beneficial Role of Lactic Acid Bacteria in Food Preservation and Human Health: A Review. Research Journal of Microbiology. 5:1213-1221.
[82]	Caplice, E. and Fitzgerald, G.F. (1999). Food fermentations: Role of microorganisms in food production and preservation. Int. J. Food Microbiol. 50: 131-149.
[83]	Ray, B. (1992). The Need for Food Bio Preservation. In: Food Bio Preservatives of Microbial Origin, Ray, B. and M. Daeschel (Eds.). CRC Press, Boca Raton, Florida, pp: 1-23.
[84]	Mutegi, E., Sagnard, F., Muraya, M., Kanyenji, B., Rono, B., Mwongera, C., Marangu, C., Kamau, J., Parzies, H., de Villiers, S., Semagn, K., Traoré, P. and Labuschagne, M. (2010). "Ecogeographical distribution of wild, weedy and cultivated Sorghum bicolor(L.) Moench in Kenya: implications for conservation and crop-to-wild gene flow". Genetic Resources and Crop Evolution 57(2): 243-253.
[85]	http://www.dpi.qld.gov.au/4790_20318.htm.
[86]	Dweikat, I. (2017). Sweet sorghum is a drought-tolerant feedstock with the potential to produce more ethanol/acre than corn". Department of Agronomy and Horticulture, University of Nebraska-Lincoln. Retrieved 2017-03-02.
[87]	https://en.wikipedia.org/wiki/Sorghum
[88]	Dillon, S.L., Shapter, F.M., Henry, R.J., Izquierdo, L. and Lee, L. S. (2007). "Domestication to Crop Improvement: Genetic Resources for Sorghum and Saccharum (Andropogoneae)". NIH. PMC 2759214
[89]	https://en.wikipedia.org/wiki/Sorghum_bicolor.
[90]	Sharma, O.P. (1993). Plant Taxonomy. Tata McGraw-Hill. p. 439.
[91]	National Research Council (1996). "Sorghum". Lost Crops of Africa: Volume I: Grains. Lost Crops of Africa. 1. National Academies Press. ISBN 978-0-309-04990-0. Retrieved 2008-07-18.
[92]	Edema, M. O., Sanni, A. I. (2006). Micro-population of fermenting maize meal for sour maize bread production in Nigeria. Nigerian Journal of Microbiology. 20(2): 937-946.
[93]	Lonner, C., Welander, T., Molin, N. andDostalek, M. (1986). The micro-flora in a sourdough started spontaneously on typical Swedish rye meal. Food Microbiology. 3: 3-12.
[94]	Fawole, M.O. and Oso, B.A. (2007). Characterisation of Bacteria: Laboratory Manual of Microbiology. Revised Ed. Spectrum Book Limited 24-33 Pp. Ibadan, Nigeria.
[95]	G Ottogalli, A Galli, R Foschino - 1996. Italian bakery products obtained with sour dough: characterization of the typical microflora. Journal of Advances In Food Sciences, 18 (5-6) 131-144.
[96]	Odunfa, S. A., & Adeleye, S. (1985). Microbiological changes during the traditional production of Ogi-baba, a West African fermented sorghum gruel. Journal of Cereal Science, 3, 173-180.
[97]	Mbata, T. I., Ikenebomeh, M. J., & Alaneme, J. C. (2009). Studies on the microbiological, nutrient composition and antinutritional contents of fermented maize flour fortified with bambara groundnut (Vigna subterranean L.). African Journal of Food science, 3(6), 165-171.
[98]	Edema, M. O., & Sanni, A. I. (2008). Functional properties of selected starter cultures for sour maize bread. Food Microbiology, 25, 616-625. https://doi.org/10.1016/j.fm.2007.12.006
[99]	Hammes, W.P., Brandt, M. J., Francis, K.L., Rosenheim, J., Seitter, M. F. H. and Vogelmann, S. A. (2004). Microbial ecology of cereal fermentations. Trends in Food Science and Technology, 16(1-3): 4-11.
[100]	Wood, B.J.B. and Holzapfel, W.H. (1995). The Lactic Acid Bacteria: The Genera of Lactic Acid Bacteria, 1st edition. Chapman and Hall. London.