## 1 Introduction  
Fermentation is a traditional food processing method employed to improve nutritional and sensory qualities, shelf-life, and safety of final products, in addition to the removal of undesirable components of primary substrate [1, 2]. Diverse microorganisms are used to provide specific fermented food products. The largest group of bacteria involved in fermentation processes is lactic acid bacteria (_Lactobacillus_, _Lactococcus_, and _Pediococcus_ spp. ), yeasts (_Candidia_, _Debaryomyces_, _Hansenula_, _Pichia_, and _Saccharomyces_ spp. ), and filamentous fungi (_Amylomyces_, _Aspergillus_, _Mucor_, and _Rhizopus_ spp.) [3, 4]. LAB are widely used within the food industry, not only as health promoting cultures, but, due to their growth and metabolism, they also contribute to the safety and stability of final food products [4]. Some strains of LAB have proven beneficial effects on host health via improving intestinal microbial balance. These are called probiotics, which are defined as \"live microorganisms which when administered in adequate amounts confer a health benefit on the host\" [5]. The most common bacteria used in probiotic preparations are _Lactobacillus_ species such as _L. acidophilus_, _L. rhamnos_, _L. casein_, or _Bifidobacterium_ species such as _B. lactis_, _B. longun_, or _B. breve_[6]. Cereals and pseudocereals are highly important food sources in the human diet, and represent substantial substrates for the production of fermented foods. Generally, cereals and pseudocereals contribute to the intake of carbohydrates and, as a result, energy and dietary fiber, proteins, minerals, and vitamins, with numerous proven health effects [4]. A variety of technologies are used for cereal processing, but fermentation remains the best choice for improving the quality of proteins by increasing a number of factors, including: the available lysine, methionine, and tryptophan content; protein digestibility by reduction in protease inhibitors; starch digestibility; bioavailability of minerals (iron, zinc, calcium, magnesium) by degradation of phytate; content of B group vitamins; and content of phenolic compounds [4; 7; 8]. Many of the positive effects on human health of cereals and pseudocereals have been attributed to the presence of phenolic compounds. A valuable source of phenolics is buckwheat (_Fagopyrun esculent_ Moench), belonging to pseudocereals. Within the phenolics group, buckwheat grain contains phenolic acids (caffeic, \(p\)-cumaric, ferulic, sinapic, gallic, protocatechuic, vanillic, syringic, neochlorogenic, and chlorogenic) and flavonoids (rutin, quercetin, procyanidin B2, catechin, epicatechin gallate, vitexine, isovitexin, orientin, isorientin, and kaempfer) [9; 10; 11; 12; 13]). Polyphenols of buckwheat occur in free, soluble conjugate, and insoluble bound forms, of which the free form is predominant [14; 15]. Many additional nutraceuticalals, such as phytosterols (\(\beta\)-sitosterol, campesterol, stigmasterol, and isofucosterol), fagopyrins, and lignans also are present in buckwheat [13; 16]. The protein content in buckwheat is higher and the amino acid profile is balanced compared to those of commonly used cereals. Lysine and arginine are present in high quantities, resulting in an amino acid score of 100. Buckwheat protein contains little or no gluten, which determines its usefulness for gluten-free diet, i.e., for people suffering from coeliac disease or an allergy to gluten [11; 17]. A considerable number of studies have investigated the application of buckwheat in the production of gluten-free products and as a potential substrate for potentially functional foods. [PERSON] et al. [18] investigated buckwheat as a composite flour in the development of gluten-free breads. [PERSON] et al. [19] prepared an antidiabetic functional food from Tartary buckwheat fermented by _Lactobacillus plantarum_ TK9 and _L. paracasei_ TK1501. [PERSON] et al. [20] evaluated gluten-free muffins based on unfermented and _L. plantarum_-fermented buckwheat flour. [PERSON] et al.