The Era of Plant-Based Probiotics: An Overview of Potential Benefits and Future Aspects

Abstract

Background and Objective: Probiotics, defined as specific strains of live microorganisms, usually bacteria or yeast, play a crucial role in host health by enhancing digestive functions. Traditionally, these organisms were sourced from dairy-based fermented foods such as yogurt, cheese, and kefir; however, the rise in plant-based diets has spurred the popularity of plant-based probiotics, driven by factors such as veganism, lactose intolerance, and dairy allergies. Plant-based probiotics offer a valuable alternative that caters to diverse dietary requirements while also contributing to environmental sustainability through lower greenhouse gas emissions, reduced water consumption, and less land use. This review delves into the development, potential health benefits, future applications, and technological challenges related to the production and marketing of plant-based probiotics. Results and Conclusion: Innovative approaches have led to the creation of functional foods that combine plant sources with robust probiotic strains capable of surviving in plant-based matrices. The integration of probiotics with prebiotic fibers such as chicory and acacia, has proven to enhance viability and performance. Furthermore, plant-based probiotic products are evolving beyond beverages to encompass snacks, ready-to-eat fruits, and nuts. Nonetheless, challenges persist regarding the viability of probiotic strains during storage, the costs associated with large-scale production, and the necessity of consumer education. Regulatory frameworks are being adapted to ensure health claims attributed to probiotic products that are backed by scientific evidence. As a promising frontier in sustainable functional foods, plant-based probiotics cater to a wide range of consumer needs. Future advancements are anticipated to focus on personalized formulations and broader applications within health and wellness, alongside improved techniques to enhance probiotic stability and efficacy. Keywords: Functional foods, Non-dairy Probiotics, Plant-based probiotics, Sustainable nutrition, Vegan health, Gut microbiome, Eco-friendly foods   Introduction   Probiotics are live microorganisms that confer health benefits to the host when administered in adequate quantities [1]. These microorganisms exert beneficial effects via production of antimicrobial compounds, inhibition of pathogenic bacteria, and the generation of essential metabolites, including vitamins and short-chain fatty acids (SCFAs), thereby contributing to the overall well-being of the host [2]. The growing interest in probiotics is reflected in both scientific research and industry. Historically, dairy matrices have facilitated the growth and survival of probiotics, leading to their predominant use in products like yogurt, kefir, and cheese [3]. However, the reliance on dairy probiotics poses limitations that restrict their access to broader consumer groups. Among the most well-known probiotic species are members of the lactic acid bacteria (LAB) group, comprising strains such as Lactobacillus acidophilus, Lacticaseibacillus casei, Lactobacillus crispatus, Bacillus coagulans, Lactobacillus delbrueckii subsp. bulgaricus, Limosilactobacillus fermentum, Ligilactobacillus gasseri, Lactobacillus helveticus, Ligilactobacillus johnsonii, Lacto-coccus lactis, Lacticaseibacillus paracasei Lactiplanti-bacillus plantarum, Limosilactobacillus reuteri, Lacticasei-bacillus rhamnosus[4]. Traditionally, these beneficial microorganisms are sourced from fermented dairy products, including kefir, yogurt, and curd. The growing demand for vegan foods, driven by health considerations, the prevalence of lactose intolerance, and increasing awareness of milk protein allergies, has fostered a shift toward non-dairy alternatives, notably in Asia and parts of Africa, where access to dairy products is limited [5]. Consumers are increasingly seeking sustainable probiotic delivery systems that align with ethical and environmental values [6]. Furthermore, eco-conscious consumers like to seek more sustainable probiotic delivery systems [7]. Figure 1 shows the classification of various probiotic foods. Simultaneously, developments in fermentation technologies and food science have demonstrated the potential of plant-based matrices, such as cereals, legumes, fruits, vegetables, and plant-based milks, as efficient probiotic carriers. In addition to meeting dietary requirements, these substrates offer extra phytochemicals, dietary fiber, and bioactive compounds that could complement the effects of probiotics [8]. By offering unique tastes, textures, and health benefits, plant-based probiotic formulations can appeal to a large market. Despite these promising trends, technological challenges remain unresolved. For example, probiotic viability, stability, sensory optimization, and regulatory frameworks for plant-based products are a few of them. Moreover, further research and developments are needed to confirm the efficacy of particular strains in plant-based matrices, with an emphasis on consumer demand, technological advancements, and health applications. This review aims to provide a comprehensive overview of the emerging field of plant-based probiotics, highlighting the drivers of consumer demand, technological innovations, and health applications while critically examining the current limitations and future directions. Growing Demand Drivers 2.1. Vegan and dairy-free probiotic trends The growing demand for lactose-free, cholesterol-free, and vegan foods has led to innovations in non-dairy probiotic systems. Researchers and industries are exploring plant-based alternatives like tree nuts, cereals, fruits, and vegetables as alternatives to traditional dairy substrates [9]. Due to their rich nutrient and prebiotic content, tree nuts such as almonds and cashews are emerging as promising fermentation substrates. Major challenges, such as emulsion stability and microbial viability, are being addressed using encapsulation techniques, natural stabilizers, and pH control [9]. For instance, traditional dairy products such as kefir, renowned for its health-promoting components like GABA (Gamma-aminobutyric acid), are now being reformulated using soy, rice, oat, and coconut bases. Although these alternatives may vary in taste and texture, they still provide metabolic advantages [10]. Recent advancements have introduced specific, well-characterized microbial strains specially designed for use with plant substrates, ensuring safety, functional efficiency, and reproducibility criteria. Targeted fermentation leveraging local agricultural resources can enhance the nutritional and therapeutic potential of plant-based probiotic foods [11]. Fruit- and vegetable-based probiotic beverages are gaining traction due to their nutritional variety and bioactive compounds that enhance shelf-life and functional value. Nevertheless, commercialization is still limited, necessitating further technological innovations [12]. Fermented plant foods such as olives, vegetable juices, and pickled products, exhibit excellent potential as probiotic carriers due to their supportive matrices that enhance microbial adhesion and viability during controlled processing [10]. Nutritional evaluations indicate that vegan substitutes for dairy products like yogurt and cheese typically contain lower protein but higher fat and carbohydrate content. However, allergen risks from ingredients such as soy, nuts, and gluten pose challenges for product formulation. Clean labeling, improved protein profiles, and hypoallergenic options are vital for enhancing consumer acceptance [6]. Utilizing seasonal and regionally sourced substrates meets consumer demand for sustainable foods while also reducing production costs [13]. Transitioning from lab-scale innovation to industrial scalability necessitates multidisc-ciplinary collaboration encompassing microbiological, technological, and economic expertise. 2.2 Gut-health awareness The gut microbiome plays a pivotal role in maintaining health by supporting metabolic, immunological, and protective functions; however, awareness of its importance among the public remains limited, especially among children and adults [14] across many regions. An educational initiative conducted at a science fair in Kuala Lumpur, Malaysia, aimed to raise awareness about gut microbiota by engaging 324 participants aged 5 to 64 through quizzes and informational displays. Post-session, 77.9% of participants reported increased awareness of gut microbiota, with 85.3% expressing a willingness to incorporate more fruits and vegetables into their diets. Additionally, 60.5% indicated an intention to bring fruit for breaks in school or at work [14]. Research focusing on parental awareness of infant gut health uncovered significant gaps in knowledge provided by healthcare professionals. A survey of 933 parents, particularly those with preterm infants or those born via cesarean section, revealed a general lack of awareness concerning the connection between delivery mode and gut microbiome development [15]. Most parents did not receive adequate information on the significance of infant gut health, nor did they understand the roles of prebiotics and probiotics. This highlights the urgent need for targeted educational initiatives to inform parents about promoting their infant’s gut microbiome. Alongside traditional fermented foods and probiotic supplements, there is growing recognition of the role of fruits and vegetables as prebiotics, representing a promising avenue for encouraging healthier gut microbiota [6]. These educational efforts underscore the critical importance of public health initiatives in facilitating long-term dietary changes and making gut health knowledge more accessible to wider populations.   2.3 Sustainability awareness among consumers Heightened environmental concerns have significantly influenced consumer preferences within the food and beverage sectors. Plant-based dairy alternatives are gaining attraction, not only for their health benefits but also due to their reduced environmental footprint. Compared to conventional dairy production, plant-based alternatives typically use less land, water, and produce fewer greenhouse gases, marking them as a more sustainable choice [7]. This aligns with the values of eco-conscious consumers, particularly among younger demographics, who actively seek products that uphold ecological balance and mitigate climate impacts. As sustainability emerges as a driving force behind food innovation, the shift toward plant-based options reflects both ethical consumption trends and efforts to combat environmental degradation. Emerging Sources and Innovations Plant-based probiotics (PBPs) are sourced from various plant matrices serving as effective carriers for probiotic delivery. These products address the drawbacks of dairy-based options and are suitable for individuals with restrictive diets requiring probiotics. Major plant sources contributing to the development of non-dairy probiotics include cereals, legumes, fruits, vegetables, and plant-based milks [16]. Cereal-Based Products Cereals are rich in protein, carbohydrates, vitamins, minerals, and fiber. Cereal grains such as maize, sorghum, millet, oats, barley, wheat, and rye are being utilized for the production of probiotic-rich foods, incorporating probiotic strains to enhance consumer health benefits. Legume-Based Products: Legumes (e.g., chickpeas, beans, lupins, soybeans) boast high levels of resistant starch and galactooligosaccharides, known for stimulating the growth and survival of probiotics. Vegetable-Based Products: Vegetables are abundant in carbohydrates, vitamins, minerals, and health-promoting compounds such as phytochemicals and phytonutrients. Commonly used substrates include carrots, cabbage, tomatoes, and beets, which are utilized to manufacture probiotic products employing LAB species like L. acidophilus, L. plantarum, and B. longum. Fruit-Based Probiotic Products: Fruit juices (e.g., apple, pineapple, mango, orange) serve as alternative vehicles for delivering probiotics. These juices offer health benefits and refreshing flavors enjoyed by diverse age groups, being rich in sugars and bioactive compounds that probiotics can utilize [8].   Non-Dairy milk substitutes: Traditional milk products are increasingly being replaced by plant-based alternatives composed mainly of nuts and cereals, such as soy, almond, rice, and oat milks, each of which confer various health benefits [10]. These alternatives are regarded as functional foods, delivering essential nutrients that can aid in disease prevention [16]. 3.1 Traditional sources of fermented plant foods Fermentation stands as an age-old, cost-effective technique for preserving food, leveraging the growth and metabolic activities of microorganisms. Traditional fermented plant-based foods are valued across cultures for their flavor, health benefits, and natural preservative properties, and they serve as abundant sources of probiotics. Today, they are gaining recognition as effective non-dairy probiotic vehicles within vegan diets and functional food innovations [17]. Key examples of fermented foods and their functional benefits include: Kimchi is a fermented vegetable dish prepared from vegetables, usually Chinese cabbage (Napa cabbage), Korean radish, and a variety of seasonings (ginger, garlic, salt, red chilli pepper, fish sauce/shrimps, etc.). This is a popular side dish in East Asian nations like Korea, Japan, and China. It acts as a probiotic vegetable food product that has rich nutritional qualities. Kimchi is also considered to be the source of LAB (L. plantarum, L. brevis). It helps to boost digestive health, improve immune system and mental health. Other beneficial properties of kimchi include cholesterol lowering activity, anti-obesity, anti-cancer, antioxidant, and anti-atherosclerotic properties [18]. Sauerkraut is a traditional fermented vegetable item prepared from cabbage. It is produced by spontaneous fermentation of cabbage that mainly involves hetero-fermentative LAB [19]. This is also known as German kraut and is very popular in European countries. Natural, unprocessed sauerkraut contains beneficial probiotic micro-organisms like LAB (L. plantarum, Leuconostoc mesenteroides) [20]. From these foods, organic acids are produced by metabolizing sugars in the raw materials, altering flavors, prolonging its shelf life and producing B vitamins, such as folate (B9) riboflavin (B2), and other healthy components such as isothiocyanates and glycosylates. These compounds exhibit anti-inflammatory and anticancer properties which modulates specific cellular pathways and showing antioxidant activity which neutr-alizes the damaging effects of free radicals [8]. Tempeh is a nutrient-rich fermented legume food derived from soybeans and commonly consumed in Southeast Asia, especially in Indonesia and Malaysia. The fermentation process involves growth of mold, Rhizopus spp. which transforms soybeans into a white firm cake-like product as enzymes break down complex nutrients in soybeans into simpler forms, enhancing the bioavailability of proteins, fiber, and other nutrients. Consumption of Tempeh has been linked to various health advantages including antidiabetic effects, reduced risk of cardiovascular diseases, cholesterol-lowering properties, improved cognitive function, antitumor and anticancer properties, anti-aging effects and improved gut health [21]. Miso is a Japanese salty and flavorful fermented paste made by fermenting soybeans with salt and a fungus viz., Aspergillus oryzae (koji), Lactobacillus sp. along with soybeans and other ingredients such as barley, rice, and rye. It is typically salty and is considered as a good source of protein, fiber and vitamins (especially vitamin K), minerals, plant compounds, manganese, and copper. This helps to promote digestion, reduce cancer, obesity, high blood pressure and also helps regulate cholesterol levels [22]. Natto is another fermented soybean product, containing the bacterial strain- B. subtilis. It is typically mixed with rice and served with breakfast. It has a distinctive smell, slippery texture, and strong flavor, rich in protein, vitamin K2 and is good for bone and cardiovascular health [22]. Kombucha is a probiotic drink that originated in China which was made by fermenting sweet tea to produce a tangy and fizzy beverage. Known for its distinctive sour taste, kombucha is believed to have detoxifying properties. D-glucaric acid in kombucha is linked to liver detoxification, helping bind and eliminate harmful compounds from the body. The drink also contains antioxidants, including ascorbic acid, gluconic acid, and polyphenols, which help combat reactive oxygen species, reduce oxidative stress, and may offer protective benefits against degenerative diseases such as atherosclerosis and Alzheimer's disease [8]. Pickles are an important dish, notably in India, US, Russia etc. Even though a variety of vegetables are used for pickling, cucumbers are considered as one of the most traditional options. The fermentation process for pickle production relies primarily on naturally occurring lactic acid bacteria, notably L. plantarum and L. brevis. As bacteria utilize the carbohydrates in cucumbers which help to generate lactic acid, it imparts a characteristic tangy flavor and inhibit the proliferation of pathogens and spoilage microorganisms. The probiotic content of pickles holds potential health benefits, such as regulating blood sugar levels and exhibiting anti-cancer properties [8]. The figure 2 shows the health benefits of fermented plant-based foods having probiotic potential. 3.1.1 Microbial composition and fermentation mechanism The microbial composition in fermented plant foods primarily includes bacteria, yeasts, and moulds, of which Lactobacillus, Bifidobacterium, Acetobacter, and Saccharomyces are the predominant species. These microorganisms play crucial roles in fermentation, influencing the characteristics of the food and metabolite production [23]. The action of enzymes and activity of microorganisms may induce changes in the nutritional properties and bioactive compound content, compared to the raw substrate [24]. Fermentation mechanisms are key to developing flavor, texture, nutritional value, and probiotic functionality. Some types of fermentation involved include: (1) Lactic acid fermentation, which is involved in the formation of kimchi, sauerkraut and pickles. Some of the strains include Lactobacillus, Leuconostoc, Pediococcus, and Weissella. The mechanism involves conversion of glucose to pyruvate to lactic acid, which inhibits pathogens, and preserves the food. (2) Alcoholic Fermentation, which is involved in the formation of kombucha and certain vegetable-based beverages, is carried out using Saccharomyces cerevisiae. The mechanism involves conversion of sugars into ethanol and carbon dioxide. In kombucha, a synbiotic culture of bacteria and yeast (SCOBY) are used for its production. (3) Acetic acid fermentation that is also involved in kombucha formation (utilizing the strain   Komagataeibacter xylinus) the oxidation of ethanol to acetic acid occurs under aerobic conditions [25]. 3.1.2 Challenges associated with probiotic viability The growing market for vegan probiotics faces several major challenges, including environmental factors (pH, temperature, oxygen level, and the presence of secondary metabolites) and manufacturing processes (including heat treatment and storage conditions) that may affect probiotic viability [26]. Strategies to ensure proper viability include selecting resilient strains, implementing encapsulation, enriching substrates with prebiotics (synbiotics), managing controlled fermentation, and adhering to strict packaging and cold-chain processes [27]. 3.2 Novel strains being optimized for plant matrices In functional food production, a critical consideration is given to the food matrix, which serve as the carrier for probiotic microorganisms, and provide a supportive environment for their growth and survival. The food matrix should also protect viable probiotic cells to ensure survival during passage through the gastrointestinal (GI) tract, thus allowing the appropriate gut colonization. These steps are essential for achieving the intended probiotic health benefits for the host [28]. GABA is a non-protein amino acid, which plays a significant role as an inhibitory neurotransmitter in the mammalian central nervous system. It is been reported that GABA is associated with mammalian behavior by regulating stress and anxiety, modulating cognitive and brain functions, promoting sleep, and enhancing mood [29]. A novel probiotic GABA drink was created using brown rice as the main base ingredient, incorporating L. pentosus 9D3, a GABA-producing strain derived from Thai pickled weed [29]. L. plantarum ITM21B (LMG P-22033) and L. paracasei IMPC2.1 (also quoted as LMG-P22043) survived on brined artichokes for at least 90 days and the anchorage of bacterial strains on the vegetable tissues improved their survival in a simulation of GI digestion [30]. Probiotic drink was developed by combining extracts of medicinal plants which provide significant health benefits. A study reported by Eksiri et al 2017 showed that the produced probiotic drink containing apple juice, Pussy willow and Echium amoenum, glucose and whey powder which was a favorable medium for the growth of L. casei and L. rhamnosusto [31]. A combination of emerging strains such as Akkermansia muciniphila with polyphenol rich plant matrices (grapes, berries) enhance growth of the organism and has demonstrated to improve colonic inflammation and metabolic disorders and