**4. Soybean fermentation using mushroom mycelia**

The legume soybean is highly proteinaceous (36% protein in dried beans), rich in major nutrients essential for human nutrition and can potentially be a good replacement for animal-derived proteins [38–41]. It can be used both in fermented and

#### **Figure 4.**

*Activation of NGF synthesis with wild* H. erinaceum *and* H. ramosum *mycelia [9]. NGF levels in various parts of the brain were measured after 14 days of repeated oral administration of* H. erinaceum *and* H. ramosum mycelia *(300 mg/kg). 1, Cortex; 2, striatum; and 3, hippocampus. Data are expressed as the mean ± SEM. \*p < 0.05, compared with vehicle (Student's test).*

*Medicinal Mushroom Mycelia: Characteristics, Benefits, and Utility in Soybean Fermentation DOI: http://dx.doi.org/10.5772/intechopen.102522*

#### **Figure 5.**

*Effect of varying concentrations of wild* H. ramosum *mycelia on NGF synthesis in different parts of mouse brain [9]. 1, Cortex; 2, striatum; and 3, hippocampus. Data are expressed as the mean ± SEM. \*p < 0.05 and \*\*p < 0.01, compared with vehicle (Student's test).*

non-fermented forms [42]. While soybeans are rich in flavonoid groups such as genistein, daidzein, and glycitein isoflavones that have tremendous health benefits [43], they are not easily absorbed and incorporated in their natural glycosylated forms unless hydrolyzed by the microflora of the intestine through their beta-glucosidase production [44]. Isoflavones have health benefits against several diseases and hormone-related issues [45–48]. The easily absorbable form of flavones is the aglycon form, which is abundant in fermented sources of soybean, such as tempeh, miso, and natto [49].

Mushroom mycelia can be used as a source of beta glucosidase to convert isoflavone glycosides to their aglycon form. For example, *G. lusidum*, belonging to the basidiomycetes group, has been shown to increase serum concentration of the aglycon form of isoflavones in soybeans [50].

Studies from our laboratory investigated the health effects of fermentation using mushrooms, such as *G. lucidum*, *H. erinaceum*, and *H. ramosum* [10]. We measured DPPH scavenging activity, total phenolic content, antioxidant activity, alpha glucosidase inhibition, and isoflavone concentration, few major health parameters of paramount importance, in soybeans fermented with different mushroom types and compared them with non-fermented soybeans.

Soybean fermentation was carried out as described in Suruga et al. [10]. We found that *G. lucidum* was more effective in quickly fermenting soybeans compared to the other two mushroom types (**Figure 6**).

#### **4.1 Antioxidant activity of fermented soybean**

#### *4.1.1 Methods*

The DPPH radical scavenging activity and total phenolic content of fermented soybeans were analyzed using the methods described in Subsections 2.3.1 and 2.4.1. Oxygen radical absorbance capacity (ORAC) was determined using the OxiSelect™ ORAC Activity Assay Kit (Cell Biolabs Inc., San Diego, CA, USA) [51]. The assay was performed as described in Suruga et al. [10]. Briefly, fluorescence activity of the reaction mixture with antioxidant and fluorescein solution was measured after adding the free radical initiator. Increasing Trolox concentrations were used for the standard

#### **Figure 6.**

G. lucidum *was faster in fermenting soybeans compared to other types (a) Control (non-fermented soybeans); (b)*  G. lucidum*; (c)* H. erinaceum*; (d)* H. ramosum *[10].*

curve, and extracts were quantified and expressed as μmol Trolox equivalents/g of dry fermented soybean powder.
