배지의 아미노산 첨가가 꽃송이버섯 균사체 성장과 γ-aminobutyric acid (GABA) 생산에 미치는 영향

Abstract

Sparassis latifolia (formerly known as S. crispa) is a culinary-medicinal mushroom that has recently become popular in Korea, China, and Japan. S. latifolia is a good source of food and nutraceuticals, or dietary supplements, due to its rich flavor compounds and b-glucan content. Researches have particularly been done of the effect of b-glucan on anti-cancer and immuno-modulation effects using mice models and human trials. While, some researches are doing on the effect of brain function including neuroprotective effect of mushroom b-glucan. Thus it would be good for this mushroom to have much nutrients such as g-aminobutyric acid (GABA) as well as b-glucan. Biofortification is agricultural technology which can enhance some nutritions in crops. Most of all, supplying the fertilized soil or media nutrients to mushrooms is the most safe and effective way of biofortification. GABA, a non-essential and free amino acid, is one of the functional compounds. It helps increasing the cognitive function and improving the insomnia. Mushrooms have the GABA metabolism and it is related to TCA cycles which is an essential for growth. In this study, the enhancement of growth and GABA production in a medicinal and edible mushroom mycelia, S. latifolia, was hypothesized and amino acids were added as biofortification factors. S. latifolia mycelia (JF02-06) was provided by Jeonnam Forest Research Institute (Naju, Korea). To biofortify mushroom with two amino acids, one major approach can be used. Mycelia were pre-incubated on agar plate. Experiment for effect of amino acids was conducted with liquid media. Amino acid free medium was potato dextrose broth (PDB). Amino acids added were L-glutamic acid (PDBG media) and L-ornithine (PDBO media). The range of amino acids is 0.6-2.2% (w/v) and PDB media was used as negative control. The mycelial growth was measured by diameter of mycelia of solid media and dried weight of mycelia for liquid media. GABA and b-glucan content of dried mycelia were measured. GABA was extracted from dried mycelia with 0.1 N HCl and the extracts were freeze-dried. Freeze-dried extracts were derivatized with 1,4-dinitrofluorobenzen (DNFB). GABA was analyzed with HPLC equipped with a C18 column and gredient elution of mobile phase. b-Glucan content was measured using an assay kit from Megazyme. All results of this study were statistically analyzed using IBM SPSS Statistics version 23. The results were as follows: 1) The statistical analysis was conducted one-way ANOVA, and the result was F(10)=3.672, p<0.01. The growth of mycelia was determined to be 0.9±0.00 g/L in PDB media. And in PDBG and PDBO were 2.2±0.16 g/L and 1.93±0.34 g/L, respectively. 2) The statistical analysis was conducted one-way ANOVA, and the result was F(10)=20.183, p<0.001. The GABA content was 21.3±0.9 mg/100 g in PDB media. In PDBG 1.4% media, it was 115.4±30.2 mg/100 g and it was the best of all. However, the PDBO media was not effective to increasing the GABA content in mycelia. 3) The statistical analysis was conducted one-way ANOVA, and the result was F(10)=0.823, p>0.05. Amino acids have no effect on change of b-glucan content of mycelia. The b-glucan content were 39.7±1.4 mg/100 mg in PDB media, 34.4±0.2 mg/100 mg in PDBG 2.0% media and 35.2±9.2 mg/100 mg in PDBO 1.4% media. Addition of glutamic acid and ornithine positively affected the growth of S. latifolia mycelia and glutamic acid also positively affected the GABA production in mycelia. The key enzyme in GABA biosynthesis is glutamic acid decarboxylase (GAD) in GABA-shunt, a short GABA metabolism. So it seems that the glutamic acid is decarboxylated into GABA by GAD through the GABA-shunt. No degradation of GABA was observed in the addition of glutamic acid. More metabolism study should be done to elucidate the GABA-shunt of S. latifolia. The results of this study can be applied to other mushrooms production, and the biofortification-based approach can be a valuable asset in mushroom industry.