Evaluation of the Prebiotic Properties of Ganoderma lucidum and Lentinula edodes Polysaccharides in Enhancing Dairy Yeast and Bacterial Isolates

Abstract

IntroductionProbiotics are live, beneficial microorganisms that, when administered in adequate amounts, provide significant health benefits to the host. They play a vital role in maintaining and restoring gastrointestinal microbiota balance, improving digestion, modulating the immune system, and protecting against pathogenic bacteria. Prebiotics are non-digestible food components—typically fibers or complex carbohydrates—that selectively stimulate the growth and activity of beneficial gut microorganisms. By fostering a favorable environment for probiotics, prebiotics indirectly promote host health.Recently, the search for natural and cost-effective prebiotic sources has intensified. Medicinal mushrooms, particularly Ganoderma lucidum (reishi) and Lentinula edodes (shiitake), have emerged as promising candidates due to their abundance of bioactive polysaccharides. These polysaccharides not only exhibit prebiotic potential but also possess antioxidant, immunomodulatory, and anti-inflammatory properties.This study aimed to investigate the prebiotic properties of polysaccharides extracted from G. lucidum and L. edodes. Specifically, we evaluated their ability to stimulate the growth and metabolic activity of probiotic yeast and bacterial isolates obtained from traditional and industrial dairy products. These natural polysaccharides may contribute to the development of novel synbiotic products with enhanced health benefits.Materials and MethodsTwenty dairy product samples were collected and subjected to microbial isolation to obtain yeast and bacterial strains with probiotic potential. Isolates were identified using morphological, biochemical, and molecular techniques, including PCR and sequencing.Polysaccharides were extracted from the mycelium of G. lucidum and L. edodes via lyophilization and aqueous extraction. Carbohydrate content was determined using the phenol-sulfuric acid assay, while antioxidant capacity was assessed using the DPPH free radical scavenging method. FT-IR spectroscopy was employed to characterize chemical structures.The prebiotic effects of the mushroom polysaccharides were evaluated by supplementing sugar-free culture media with these extracts. Growth and metabolic activity of selected probiotic isolates were compared to the ontrols supplemented with glucose and inulin. Enzymatic and acid digestion assays were also performed to assess the stability of the polysaccharides under simulated gastrointestinal conditions.Results and DiscussionMultiple yeast and bacterial isolates were obtained from the dairy samples. Following biochemical screening, four isolates—A3, A10, B1, and B3—were selected for detailed analysis based on their probiotic potential. Antibiogram testing revealed varied resistance and sensitivity profiles.Molecular identification showed that isolate A10 was closely related to Candida tropicalis, while A3 matched Saccharomyces cerevisiae. Among the bacterial isolates, B1 was identified as Lactobacillus casei and B3 as Lactobacillus acidophilus.Polysaccharides extracted from G. lucidum and L. edodes exhibited lower reducing sugar content compared to inulin, indicating a more complex carbohydrate structure and greater resistance to enzymatic breakdown. Antioxidant assay demonstrated that, while inulin had the highest free radical scavenging activity, the mushroom polysaccharides also showed significant antioxidant properties.FT-IR spectra confirmed the presence of characteristic polysaccharide functional groups, such as hydroxyl, carboxyl, and glycosidic linkages, consistent with previous findings on medicinal mushroom polysaccharides.When added to sugar-free media, polysaccharides from both mushrooms stimulated the growth of probiotic isolates, though to a lesser extent than glucose and inulin. This suggests that while these fungal polysaccharides act as prebiotics, their fermentability and utilization by probiotics may differ from conventional prebiotics.Optimal growth conditions for the probiotic isolates were observed at pH 5 and 37°C. The ability of these isolates to thrive under such conditions, along with their positive response to mushroom polysaccharides, underscores the potential of these compounds as functional prebiotic ingredients.This study highlights the promising prebiotic and antioxidant properties of polysaccharides extracted from G. lucidum and L. edodes. These natural compounds supported the growth of beneficial probiotic yeasts and bacteria isolated from dairy products, suggesting their potential as synbiotic supplements.ConclusionIncorporating mushroom-derived polysaccharides into functional foods and dietary supplements could enhance gastrointestinal microbiota balance and promote overall health. However, further research involving in vivo animal models and human clinical trials is necessary to fully validate the health benefits and safety of these polysaccharides. Such studies will help clarify their mechanisms of action, determine optimal dosages, and assess long-term effects, paving the way for their application in health-promoting dietary and medicinal products.

Keywords

• ganoderma lucidum
• lentinula edodes
• prebiotic
• probiotic
• polysaccharide