Viability of Lactobacillus plantarum NCIMB 8826 immobilized in a cereal-legume complementary food “weanimix” with simulated gastrointestinal conditions
Introduction
Probiotics are “live microorganisms that when administered in adequate amounts confer a health benefit on the host” (FAO/WHO, 2002, p. 85) and are often incorporated into food products such as cheese, yogurt and other cereal product (Charalampopoulos et al., 2003). However, survival and viability of the bacterial cultures in a food product during processing, storage, consumption and though the gastrointestinal (GI) tract is required for their potential benefits to be realized (Chotiko & Sathivel, 2014; Fávaro-Trindade & Grosso, 2002). Therefore, it is advisable to add probiotics downstream of routine heat treatment procedures during food manufacturing (Fiocco et al., 2019). Some studies, however, have suggested that some probiotic cultures could survive extreme processing conditions (Mallidis et al., 2003; Tsevdou & Taoukis, 2011).
Different factors such as gastric acidity could also affect the survival of probiotics besides thermal and non-thermal treatments. Acid and bile tolerance are the fundamental parameters in determining the ability of probiotic bacteria to survive passage in the GI tract (Charalampopoulos et al., 2003). Different studies have shown that stomach pH could be as low as 1.5 and that the bile salt concentration in the small intestine is ~0.5% (Charalampopoulos et al., 2003; Kailasapathy & Chin, 2000) and that these values are dependent on the availability of food in the stomach. However, adequate measures are required to ensure delivery of live probiotics cultures in the GI tract (Gagliarini et al., 2019; Perez-Ramos et al., 2017; Soares et al., 2019). The use of barley and malt grain extracts and fiber as a food matrix to improve the tolerance, survival and viability of Lactobacillus plantarum in stimulated gastric juice have been reported (Michida et al., 2006). The viability of probiotic culture in the GI tract could be improved by cell immobilization which had an important role in bacterial survival (Doherty et al., 2011; Kemsawasd et al., 2016; Vitola et al., 2018).
Cell immobilization on a food-grade support is essential for bacterial survival during food processing. Basic methods of cell immobilization include (I) entrapment within a porous food matrix due to cells’ mobility until they are obstructed by the presence of other cells, (II) attachment or adsorption on a solid carrier surface by electrostatic forces or by covalent binding between the carrier and the bacteria cell membrane, (III) self-aggregation by either natural or artificial cross linking agents and (IV) mechanical containment behind a barrier (Mitropoulou et al., 2013). Immobilization techniques have been credited with many advantages and an important factor is protecting the cells against physicochemical changes due to factors such as pH, temperature and bile salts (Blaiotta et al., 2013; Doherty et al., 2010).
L. plantarum NCMB 8826, isolated from human saliva (de Vries et al., 2006), has been associated with a number of potential health benefits (Reid et al., 2019) such as modulation of gut microbiota (Sanchez et al., 2017), immunomodulation (Dong et al., 2012) and anti-inflammatory properties (Foligné et al., 2006). In pharmacokinetic studies in humans, L. plantarum NCIMB 8826 showed a higher survival capacity with a concentration reaching 108 cfu/ml in the ileum, where the target cells for vaccinations, i.e, Peyer's patches, are located and were then found in the feces after a single dose of fermented milk (Srisukchayakul et al., 2018; Vesa et al., 2000). Oral administration of L. plantarum NCIMB 8826 to healthy nonsmoking subjects in a double-blind randomized crossover study showed a decrease in epithelial barrier dysfunction by increasing scaffold protein zonula occludens (Zo-1) and transmembrane ocludin protein, which are the important proteins for strengthening tight junctions (Karczewski et al., 2010).
Cereals (such as wheat, malt, barley, rice bran extracts, and wheat bran) have been shown to be potential protectants and substrates for the growth of probiotic strains (Charalampopoulos & Pandiella, 2010; Charalampopoulos et al., 2003; Michida et al., 2006; Patel et al., 2004; Terpou et al., 2017). These studies reported that malt, barley and wheat bran could improve the viability and survival of probiotic cultures with simulated GI conditions. Weanimix is a cereal-legume blend developed by the United Nations Children's Fund and the Ghanaian government in 1987 as a complementary food to help transit infants from breast milk to semi-solid foods (Lartey et al., 1999; Nagai et al., 2009). A weanimix has not yet been investigated as a potential protectant and a food matrix for probiotic bacteria. Moreover, weanimix has been used as a complementary food for infants in many developing countries (Kumi et al., 2014). Therefore, this study evaluated the potential of three weanimix formulations used in sub-Saharan Africa as protectants and as food matrix for probiotic bacteria survival. The viability of L. plantarum NCIMB 8826 with acid and bile conditions was also studied.
Section snippets
Preparation of weanimix complementary food
Dried corn kernels (Zea mays), shelled cowpea (Vigna unguiculata), and shelled peanuts (Arachis hypogaea), were purchased from a local market in Accra, Ghana. Nonfat instant dry milk (Great Value™ Co., Bentonville, AR, USA) was purchased from a local market in Baton Rouge, LA, USA. The three raw materials (maize, cowpea and peanuts) were pan roasted separately for 20 min at 180 °C (Lodge L5SK3 Cast Iron Skillet, 8-inch, South Pittsburg, TN, USA). The roasted samples were allowed to cool down at
Proximate composition of complementary blend
The complementary blends (MC, MCP and MCPPM) had significant differences in proximate compositions as a result of the differences in weanimix formulations (Table 1). The crude protein contents of MCPPM, MCP and MC were all significantly different (p < 0.05). Fat contents of MC and MCP were significantly lower than for MCPPM. The differences in crude protein and fat contents were a result of the peanut and powdered milk. Anigo et al. (2010) observed similar results in crude protein and fat
Conclusion
Cell immobilization with the three weanimix complementary foods positively influenced the survival and viability of L. plantarum NCIMB 8826 when exposed to the simulated gastric and intestinal fluids, mimicking gastric and intestinal transit conditions such as acid and bile. The presence of fiber in the weanimix food matrices (MC, MCP and MCPPM) had an important role as a physical material for bacteria cell attachment. However, all three weanimixes had a viability >7 log CFU/g after exposure to
Author statement
Emmanuel Kyereh - Writing - Original Draft; Subramaniam Sathivel - Review & Editing.
Declaration of competing interest
Declarations of conflicts of interests: none.
Acknowledgements
The authors wish to thank Dr. Maria L. Marco, Department of Food Science and Technology, University of California, Davis for providing us with the Lactobacillus strain. This study was supported by the Borlaug Higher Education for Agriculture and Higher Education (BHEARD) with the Consultative Group on International Agricultural Research (CGIAR) fund [grant number BFS-G-11-00002] and the predecessor fund, the Food Security and Crisis Mitigation II [grant number EEM-G-00-04-00013].
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