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Biotransformation of Green Tea (Camellia Sinensis) with Yeasts and Lactic Acid Bacteria.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Biotransformation of Green Tea (Camellia Sinensis) with Yeasts and Lactic Acid Bacteria./
Author:	Rui, Wang.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
Description:	221 p.
Notes:	Source: Dissertations Abstracts International, Volume: 84-04, Section: B.
Contained By:	Dissertations Abstracts International84-04B.
Subject:	Fermentation. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29352858
ISBN:	9798352686379

Biotransformation of Green Tea (Camellia Sinensis) with Yeasts and Lactic Acid Bacteria.
Rui, Wang.

Biotransformation of Green Tea (Camellia Sinensis) with Yeasts and Lactic Acid Bacteria. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 221 p.

Source: Dissertations Abstracts International, Volume: 84-04, Section: B.

Thesis (Ph.D.)--National University of Singapore (Singapore), 2021.

This item must not be sold to any third party vendors.

Tea is one of the most consumed drinks in this world, the increasing demand of various tea products drives the innovation of tea. Nowadays, "natural" and "well-being benefits" are in the center of tea innovation and microbial fermentation is a promising natural way to modulate tea flavor and health benefits related components. As such, this project was carried out to ferment infusions of selected green tea with a number of yeasts and probiotics.The metabolic activities of Saccharomyces cerevisiae 71B mainly included converting monosaccharides and amino acids into ethanol and higher alcohols, respectively in green tea slurry. These alcohols were further transformed into esters with fruity and floral notes, which impart novel and desirable aroma characteristics to fermented tea. Besides, the reductions of some tea alkaloids were observed and the most important free amino acid in tea, L-theanine, was not metabolized by wine yeast fermentation. Tea catechins decreased whereas their secondary metabolite, gallic acid, increased accompanied with other antioxidants, resulting in the retention of antioxidant capacity in the fermented tea.Four non-Saccharomyces yeasts (Pichia kluyveri FrootZen, Torulaspora delbrueckii Prelude, Cyberlindnera saturnus var. mrakii NCYC 2251 and Torulaspora delbrueckii Biodiva) showed diverse performances in green tea fermentation. Strains Prelude and Biodiva metabolized sucrose faster; strain NCYC2251 was the only species that utilized xylose. Strain Prelude decreased the caffeine content significantly, while strain FrootZen showed the opposite trend. Biodiva and FrootZen increased the polyphenols content and the oxygen radical absorbance capacity of fermented teas. One of the key tea aroma compounds methyl salicylate was increased by 34-fold and 100-fold in P. kluyveri and C. mrakii fermented samples respectively.β-Glucosidase activity of C. mrakii was tested and its effects on aroma compound formation was verified by using exogenous β-glucosidase to treat green tea. The β-glucosidase activity assay of whole cells of C. mrakii revealed a positive correlation between yeast biomass (cell count) and β-glucosidase activity. GC-MS analysis showed that some glycosylated aroma compounds such as methyl salicylate, linalool and 2-phenylethanol increased in both enzyme-treated and fermented green tea, while some of the aroma compounds were converted into other metabolites by yeast.Green tea infusion was also used for probiotic yeast (Saccharomyces boulardii CNCM I-745), probiotic lactic acid bacteria (LAB) (Lactobacillus plantarum 299V) and the mixed culture fermentations. Co-inoculation of yeast and LAB remarkably enhanced the survival of LAB in probiotic-fermented tea. Meanwhile, co-culturing enhanced the aroma compounds generation; ethyl esters with fruity notes arose in both monocultured yeast and co-culture fermented teas. Compared to monoculture fermentations, co-fermentation elevated the amounts of methyl salicylate, geraniol and 2-phenylethyl alcohol to higher levels, and consumed lactic acid produced by L. plantarum to lower level, such creating a conducive environment for L. plantarum survival.Lastly, LC-QTOF-MS/MS was employed to analyse the non-volatile components of probiotic-fermented green teas; the complex flavone glycosides in yeast fermented and stored tea decreased significantly, together with the increases of flavone aglycones and other simpler flavone glycosides. LABfermented tea presented different flavone glycoside profiles, in which both Cglycosides and O-glycosides decreased and the flavone aglycones such as myricetin, luteolin, apigenin, kaempferol, and quercetin were further degraded.

ISBN: 9798352686379Subjects--Topical Terms:

658044
Fermentation.

Biotransformation of Green Tea (Camellia Sinensis) with Yeasts and Lactic Acid Bacteria.
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245 1 0 $a Biotransformation of Green Tea (Camellia Sinensis) with Yeasts and Lactic Acid Bacteria.
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300 $a 221 p.
500 $a Source: Dissertations Abstracts International, Volume: 84-04, Section: B.
500 $a Advisor: Shaoquan, Liu.
502 $a Thesis (Ph.D.)--National University of Singapore (Singapore), 2021.
506 $a This item must not be sold to any third party vendors.
520 $a Tea is one of the most consumed drinks in this world, the increasing demand of various tea products drives the innovation of tea. Nowadays, "natural" and "well-being benefits" are in the center of tea innovation and microbial fermentation is a promising natural way to modulate tea flavor and health benefits related components. As such, this project was carried out to ferment infusions of selected green tea with a number of yeasts and probiotics.The metabolic activities of Saccharomyces cerevisiae 71B mainly included converting monosaccharides and amino acids into ethanol and higher alcohols, respectively in green tea slurry. These alcohols were further transformed into esters with fruity and floral notes, which impart novel and desirable aroma characteristics to fermented tea. Besides, the reductions of some tea alkaloids were observed and the most important free amino acid in tea, L-theanine, was not metabolized by wine yeast fermentation. Tea catechins decreased whereas their secondary metabolite, gallic acid, increased accompanied with other antioxidants, resulting in the retention of antioxidant capacity in the fermented tea.Four non-Saccharomyces yeasts (Pichia kluyveri FrootZen, Torulaspora delbrueckii Prelude, Cyberlindnera saturnus var. mrakii NCYC 2251 and Torulaspora delbrueckii Biodiva) showed diverse performances in green tea fermentation. Strains Prelude and Biodiva metabolized sucrose faster; strain NCYC2251 was the only species that utilized xylose. Strain Prelude decreased the caffeine content significantly, while strain FrootZen showed the opposite trend. Biodiva and FrootZen increased the polyphenols content and the oxygen radical absorbance capacity of fermented teas. One of the key tea aroma compounds methyl salicylate was increased by 34-fold and 100-fold in P. kluyveri and C. mrakii fermented samples respectively.β-Glucosidase activity of C. mrakii was tested and its effects on aroma compound formation was verified by using exogenous β-glucosidase to treat green tea. The β-glucosidase activity assay of whole cells of C. mrakii revealed a positive correlation between yeast biomass (cell count) and β-glucosidase activity. GC-MS analysis showed that some glycosylated aroma compounds such as methyl salicylate, linalool and 2-phenylethanol increased in both enzyme-treated and fermented green tea, while some of the aroma compounds were converted into other metabolites by yeast.Green tea infusion was also used for probiotic yeast (Saccharomyces boulardii CNCM I-745), probiotic lactic acid bacteria (LAB) (Lactobacillus plantarum 299V) and the mixed culture fermentations. Co-inoculation of yeast and LAB remarkably enhanced the survival of LAB in probiotic-fermented tea. Meanwhile, co-culturing enhanced the aroma compounds generation; ethyl esters with fruity notes arose in both monocultured yeast and co-culture fermented teas. Compared to monoculture fermentations, co-fermentation elevated the amounts of methyl salicylate, geraniol and 2-phenylethyl alcohol to higher levels, and consumed lactic acid produced by L. plantarum to lower level, such creating a conducive environment for L. plantarum survival.Lastly, LC-QTOF-MS/MS was employed to analyse the non-volatile components of probiotic-fermented green teas; the complex flavone glycosides in yeast fermented and stored tea decreased significantly, together with the increases of flavone aglycones and other simpler flavone glycosides. LABfermented tea presented different flavone glycoside profiles, in which both Cglycosides and O-glycosides decreased and the flavone aglycones such as myricetin, luteolin, apigenin, kaempferol, and quercetin were further degraded.
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