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Comparison of volatile and non-volatile metabolites in rice fermented by 12 different lactic acid bacteria

Comparison of volatile and non-volatile metabolites in rice fermented by 12 different lactic acid bacteria
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대학원 식품공학과
이화여자대학교 대학원
Rice consumption in Korea has been decreased nowadays. Also, consumers who find dairy replacement instead of cow’s milk are increasing. Processed rice products has been considered a solution of this problems. Rice beverage fermented by lactic acid bacteria can not only increase rice consumption, but also have potential of dairy replacement. This study investigated that volatile and non-volatile metabolites in rice fermented by 12 different lactic acid bacteria. Volatiles of fermented rice samples were analyzed using GC-MS combined by solid phase micro-extraction (SPME) and non-volatile metabolites in fermented rice were analyzed using GC-TOF/MS with solvent extraction (water : methanol : chloroform=8:2:1). A total of 47 volatile compounds, including 3 acids, 5 aldehydes, 4 esters, 4 furans derivatives, 6 ketones, 13 alcohols, 10 benzene and benzene derivatives, 1 hydrocarbons and 1 terpene, were found, whereas a total of 37 non-volatile metabolites, including 17 amino acids, 7 organic acids and 13 carbohydrates, were analyzed. In general, there was a significant difference in the profiles of volatile and non-volatile metabolites between homo-/facultatively heterofermentative lactic acid bacteria and obligatorily heterofermentative. On PLS-DA score plot, only Lactobacillus sakei sample was discriminated from other 11 samples. Especially, furans contributed this differentiation, being observed high amounts of furans in Lactobacillus sakei. On the PLS-DA score plot besides Lactobacillus sakei, the 11 samples were separated into homo-/faculatively hetero one and obligatorily heterofermentative LAB by component 1. Several alcohols (heptan-2-ol, ethanol, 3-methylbutan-1-ol, (E)-hept-2-en-1-ol) and ketones (butan-2-one, 6-methylhep-5-en-2-one, 3-hydroxybutan-2-one, butane-2,3-dione, propan-2-one) were highly contributed to discriminate samples. The content of ethanol was quite higher in obligatorily heterofermentative than homo/facultatively hetero LAB. Especially, levels of butane-2,3-dione (diacetyl) and 3-hydroxybutan-2-one (acetoin), which are carbonyl compound, were much higher in homo-/facaltatively heterofermentative than obligatorily heterofermentative one. Lactobacillus paracasei species, classified as facultatively hetero-, produced the highest butane-2,3-dione and 3-hydroxybutan-2-one among 12 samples. Moreover, mannitol were detected in all obligatorily heterofermentative LAB besides Weissella cibaria, while absence in all facultatively hetero-/homo LAB samples.;오늘날 한국의 쌀 소비량은 줄어들고 있으며 유제품을 대체할 수 있는 제품을 찾는 소비자는 증가하고 있다. 젖산균에 의해 발효 된 쌀 음료는 쌀 섭취량을 증가시킬 뿐만 아니라 유제품 대체식품으로 발전 가능성이 높다. 본 연구는 12 가지 유산균에 의해 발효 된 쌀의 휘발성 및 비휘발성 대사산물을 분석하였다. 발효된 쌀 시료의 휘발성 물질을 GC-MS와 SPME (solid phase micro-extraction)를 이용하여 분석하였으며, 발효 쌀의 비휘발성 대사산물은 GC-TOF / MS를 사용하여 용매 추출(물 : 메탄올 : 클로로포름 = 8 : 2 :1) 하였다. 결과적으로 3종의 acids, 5종의 aldehydes, 4종의 esters, 4종의 furans derivatives, 6종의 ketones, 13종의 alcohols, 10종의 benzene and benzene derivatives, 1종의 hydrocarbons, 1종의 terpene을 포함하는 총 47종의 휘발성 물질이 분석되었다. 또한 17종의 amino acids, 7종의 organic acids, 13종의 carbohydrates를 포함하는 총 37종의 비휘발성물질이 검출되었다. homo-/facultatively heterofermentative 유산균과 obligatorily heterofermentative 유산균의 휘발성, 비휘발성 대사산물 프로파일에는 유의적인 차이가 있었다. PLS-DA score plot에서 Lactobacillus sakei를 사용한 시료는 다른 11개의 시료와 구별되었다. 이는 Lactobacillus sakei에서 특히 많이 검출된 furans의 기여도가 높은 것으로 나타났다. Lactobacillus sakei를 제외한 PLS-DA에서 성분 1에 의해 homo-/facultatively heterofermentative 유산균과 obligatorily heterofermentative 유산균으로 분리되었다. 여러 알코올 (heptan-2-ol, ethanol, 3-methylbutan-1-ol, (E)-hept-2-en-1-ol) 및 케톤 (butan-2-one, 6-methylhep-5-en-2-one, 3-hydroxybutan-2-one, butane-2,3-dione, propan-2-one)은 이러한 분리에 크게 기여하였다. ethanol함량은 homo-/facultatively heterofermentative 유산균보다 obligatorily heterofermentative 유산균에서 훨씬 높게 나타났다. 반면에 butane-2,3-dione (diacetyl) and 3-hydroxybutan-2-one (acetoin)은 homo-/facultatively heterofermentative 유산균에서 훨씬 높았다. 특히 Lactobacillus paracasei를 사용한 시료의 경우에 12개 시료들 중에서 butane-2,3-dione (diacetyl) and 3-hydroxybutan-2-one (acetoin)이 가장 높았다. Mannitol은 모든 homo-/facultatively heterofermentative 유산균에서 검출되지 않았으나 obligatorily heterofermentative 유산균에서는 Weissella cibaria를 제외한 모든 시료에서 검출되었다.
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