Growth studies of potentially probiotic lactic acid bacteria in cereal-based substrates

Abstract

Aims:The overall growth kinetics of four potentially probiotic strains (Lactobacillus fermentum, Lact. reuteri, Lact. acidophilus and Lact. plantarum) cultured in malt, barley and wheat media were investigated. The objectives were to identify the main factors influencing the growth and metabolic activity of each strain in association with the cereal substrate. Methods and Results: All fermentations were performed without pH control. A logistic-type equation, which included a growth inhibition term, was used to describe the experimental data. In the malt medium, all strains attained high maximum cell populations (8AE10-10AE11 log 10 cfu ml )1 , depending on the strain), probably due to the availability of maltose, sucrose, glucose, fructose (approx. 15 g l )1 total fermentable sugars) and free amino nitrogen (approx. 80 mg l )1 ). The consumption of sugars during the exponential phase (10-12 h) resulted in the accumulation of lactic acid (1AE06-1AE99 g l )1 ) and acetic acid (0AE29-0AE59 g l )1 ), which progressively decreased the pH of the medium. Each strain demonstrated a specific preference for one or more sugars. Since small amounts of sugars were consumed by the end of the exponential phase (17-43%), the decisive growth-limiting factor was probably the pH, which at that time ranged between 3AE40 and 3AE77 for all of the strains. Analysis of the metabolic products confirmed the heterofermentative or homofermentative nature of the strains used, except in the case of Lact. acidophilus which demonstrated a shift towards the heterofermentative pathway. All strains produced acetic acid during the exponential phase, which could be attributed to the presence of oxygen. Lactobacillus plantarum, Lact. reuteri and Lact. fermentum continued to consume the remaining sugars and accumulate metabolic products in the medium, probably due to energy requirements for cell viability, while Lact. acidophilus entered directly into the decline phase. In the barley and wheat media all strains, especially Lact. acidophilus and Lact. reuteri, attained lower maximum cell populations (7AE20-9AE43 log 10 cfu ml )1 ) than in the malt medium. This could be attributed to the low sugar content (3-4 g l )1 total fermentable sugar for each medium) and the low free amino nitrogen concentration (15AE3-26AE6 mg l )1 ). In all fermentations, the microbial growth ceased at pH values (3AE73-4AE88, depending on the strain) lower than those observed for malt fermentations, which suggests that substrate deficiency in sugars and free amino nitrogen contributed to growth limitation. Conclusions: The malt medium supported the growth of all strains more than barley and wheat media due to its chemical composition, while Lact. plantarum and Lact. fermentum appeared to be less fastidious and more resistant to acidic conditions than Lact. acidophilus and Lact. reuteri. Significance and Impact of the Study: Cereals are suitable substrates for the growth of potentially probiotic lactic acid bacteria.

Vegetable milks and their fermented derivative products

“…With regards to the fermentation time, much longer is usually needed than during standard cow milk yogurt production, since potential probiotic bacteria (type of bacteria currently chosen to develop these foodstuffs due to the added value on the final product) have more complex nutritional requirements (Severson, 1998), especially when growing in vegetable matrices. The reported fermentation times have been found to be around 16-24 h if no growth enhancers are used in the formulation (Dimitris Charalampopoulos & Pandiella, 2010;D Charalampopoulos, Pandiella, & Webb, 2002;Coda, Rizzello, & Gobbetti, 2010;Correa, Castro, & Saad, 2008;Blaiotta, Di Capua, Coppola, & Aponte, 2012;Cui, Chen, Wang, & Han, 2013;Gokavi et al, 2005;Gupta, Cox, & Abu-Ghannam, 2010;Martensson, Oste, & Holst, 2002). The fermentation procedure finishes when the pH value of milks reaches 4.2-4.5.…”

Development of a sweet whey-based medium for culture of Lactobacillus

“…Rich and complex media, like MRS (De Man et al, 1960) or M17 (Terzaghi and Sandine, 1975) (Kurbanoglu, 2004), corn steep liquor (Cornelius et al, 1996;Marcela et al, 2016), whey protein hydrolysates (Mc Comas and Gilliland, 2003;Watanabe et al, 2004), malt sprout extract, casein hydrolysates (Vahvaselkä and Linko, 1987;Chiarini et al, 1992;Horáčková, 2014), baker's yeast cells (Altaf et al, 2007), vegetal substrates (Gardner et al, 2001;Nancib et al, 2001;Charalampopoulos et al, 2002;Djeghri-Hocine et al, 2006;Djeghri-Hocine et al, 2007a), sugarcane juice (Preeti et al, 2016), Palmyra palm jaggery (Reddy Tadi et al, 2017), and de-lipidated egg yolk (DjeghriHocine et al, 2007b). The most efficient nitrogen source seems to be yeast extract (Aeschlimann and Von Stokar, 1990;Arasaratnam et al, 1996;Göksungur and Gűvenç, 1997;Guha et al, 2013;Vethakanraj et al, 2013).…”

Recent Application of Probiotics in Food and Agricultural Science

“…Indeed, numerous cereal-based products in the world require a lactic fermentation, often in association with yeast or molds. Cereals are good substrates for the growth of probiotic strains and due to the presence of non-digestible components of the cereal matrix may also serve as prebiotics [114,115]. Due to the complexity of cereals, a systematic approach is required to identify the factors that enhance the growth of probiotic in cereals [116].…”

“…Also the addition of sweeteners aspartame, sodium cyclamate, saccharine and Huxol (12% cyclamate and 1.2% saccharine) had no effect on the dynamics of the fermentation process and on the viability of the starter culture during product storage [93]. Charalapompoulos and others have done experiments with different cereals to determine the main parameters that need to be considered in the growth of probiotic microorganisms, defining them as follows: the composition and processing of cereal grains, the substrate formulation, the growth capability and productivity of the starter culture, the stability of the probiotic strain during storage, the organoleptic properties and the nutritional value of the final product [114]. They reported that many cereals supported the growth of probiotics with some differences.…”