Genomics Technologies for Enhanced Understanding of Robustness of LAB Starter Cultures

Genomics Technologies for Enhanced Understanding of Robustness of LAB Starter Cultures

Annereinou R. Dijkstra, Peter A. Bron
Copyright: © 2018 |Pages: 10
DOI: 10.4018/978-1-5225-5363-2.ch007
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During production and application, starter culture strains encounter several stresses. To ensure an adequate contribution to the fermentation process, starter culture strains should remain viable, justifying the increasing industrial efforts to unravel robustness characteristics of LAB starter culture strains. Nowadays, large numbers of genome sequences are publicly available, which enables the employment of several genomics technologies to increase our understanding of robustness. This aids the improvement of currently applied LAB starter culture strains and supports the industrial application of novel strains with specific desirable traits but currently inadequate robustness characteristics. This chapter explores genomics technologies for enhanced understanding of robustness of LAB starter cultures.
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Food fermentation, which involves the conversion of sugars into organic acids or alcohol by microorganisms, is performed since ancient times. For example, evidence has been found for the presence of fermented beverages as early as 6,000 B.C. in a Chinese village (McGovern, et al., 2004). Initially, food fermentation processes were used for preservation of raw food materials and were spontaneous fermentations with microorganisms present in the raw food material or on the tools applied. The endresult of such spontaneous fermentations is rather unpredictable due to variation in the microbiota of the raw material and handling of the food material. By applying back-slopping methods, where part of the fermentation endproduct is used to initiate a new fermentation, fermentation processes became more controlled (Leroy, 2004; Smid & Hugenholtz, 2010). Industrialization of food fermentation processes in the late nineteenth century led to the use of starter cultures, which were added to the raw food material, resulting in a safer and more stable product. Starter cultures are generally classified as defined or undefined. Undefined starter cultures have a complex composition of strains and originate from traditional fermentations, whereas defined starter cultures are composed of a limited amount of known strains, which are typically isolated from undefined starters (Smid, et al., 2014). Initially, these starter cultures were propagated daily, which is time-consuming and can result in shifts in the strain composition and loss of plasmid-encoded properties (Leroy, 2004; Smid, et al., 2014). The development of concentrated starter cultures, containing high amounts of one or multiple strains in frozen or dried form, enabled the direct inoculation of fermentation processes and has largely solved these issues (Leroy, 2004; Silva, Freixo, Gibbs, & Teixeira, 2011).

The majority of the commercially available bacterial starter cultures contain lactic acid bacteria (LAB) (Santivarangkna, Kulozik, & Foerst, 2007). LAB have a long history in the fermentation of various foods, e.g., vegetables, meat, cereals and milk (Leroy, 2004). Their capability to rapidly acidify food materials by the formation of lactic acid and other organic acids prevents spoilage of the food. Moreover, the formation of aroma-compounds and exopolysaccharides contributes substantially to the taste and texture of the fermented endproduct (Leroy, 2004). The group of LAB includes the genera Lactobacillus, Leuconostoc, Pediococcus, Streptococcus and Lactococcus. Lactococcus lactis is one of the most extensively used LAB in food fermentation, mainly in the production of cheese, butter and buttermilk (Leroy, 2004). Due to its importance for the dairy industry, it became one of the best studied gram-positive bacteria (Kok, Buist, Zomer, van Hijum, & Kuipers, 2005).

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