Panimomäskin entsymaattinen fraktiointi ja ligniinijakeiden mikrobiaineenvaihdunta suolistomallissa

Dissertation

Piritta Niemi

Research output: ThesisDissertationCollection of Articles

Abstract

The objectives of this thesis were to produce lignin-rich fractions from brewer's spent grain (BSG) and to study the interactions of the lignin in these fractions with colon microbiota in vitro. Different milling pre-treatments were studied to enhance enzymatic hydrolysis of BSG carbohydrates. Ball-milling, which was the most efficient treatment, increased carbohydrate solubilisation from 23 to 45 %. Thus, milling notably improved enzymatic solubility of cell wall polysaccharides but was not effective enough to enable their total hydrolysis. Two lignin-rich fractions (24 and 40 % lignin content) were obtained by enzymatic fractionation of BSG using carbohydrases and proteases. In addition, a separate alkaline extraction provided BSG-derived material with low ferulic acid content. BSG and the fractions were used to study if lignin is degraded and metabolised by colon microbiota in a metabolic model and if lignin suppresses microbial conversions in the colon. A number of mono- and dimeric phenolic metabolites were formed upon digestion of BSG and the fractions by the microbiota. It appeared that many of them were structurally lignin-related indicating their release from lignin and conversion by colon microbiota. However, the extent of lignin degradation was estimated to be low. No notable suppression of microbial conversions was detected based on the formation of linear short chain fatty acids. In addition, experiments with pure strains of lactobacilli and bifidobacteria showed no inhibition of growth by a lignin-rich fraction. Association of lignin with carbohydrates or proteinaceous material may have reduced the possible antimicrobial effects of lignin. The results of the present study provide new information on the significance of lignin as part of dietary fibre indicating its partial metabolism by colon microbiota.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Linder, Markus, Supervisor, External person
  • Poutanen, Kaisa, Advisor
  • Buchert, Johanna, Supervisor, External person
Award date15 Apr 2016
Place of PublicationEspoo
Publisher
Print ISBNs978-952-60-6699-8, 978-951-38-8403-1
Electronic ISBNs978-952-60-6700-1, 978-951-38-8404-8
Publication statusPublished - 2016
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

lignin
spent grains
brewers grains
colon
carbohydrates
Bifidobacterium
short chain fatty acids
anti-infective properties
enzymatic hydrolysis
ferulic acid
solubilization
Lactobacillus
growth retardation
solubility
fractionation
dietary fiber
proteinases
polysaccharides
pretreatment
hydrolysis

Keywords

  • brewer's spent grain
  • enzymatic fractionation
  • lignin
  • colon microbiota
  • colon metabolic model

Cite this

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title = "Panimom{\"a}skin entsymaattinen fraktiointi ja ligniinijakeiden mikrobiaineenvaihdunta suolistomallissa: Dissertation",
abstract = "The objectives of this thesis were to produce lignin-rich fractions from brewer's spent grain (BSG) and to study the interactions of the lignin in these fractions with colon microbiota in vitro. Different milling pre-treatments were studied to enhance enzymatic hydrolysis of BSG carbohydrates. Ball-milling, which was the most efficient treatment, increased carbohydrate solubilisation from 23 to 45 {\%}. Thus, milling notably improved enzymatic solubility of cell wall polysaccharides but was not effective enough to enable their total hydrolysis. Two lignin-rich fractions (24 and 40 {\%} lignin content) were obtained by enzymatic fractionation of BSG using carbohydrases and proteases. In addition, a separate alkaline extraction provided BSG-derived material with low ferulic acid content. BSG and the fractions were used to study if lignin is degraded and metabolised by colon microbiota in a metabolic model and if lignin suppresses microbial conversions in the colon. A number of mono- and dimeric phenolic metabolites were formed upon digestion of BSG and the fractions by the microbiota. It appeared that many of them were structurally lignin-related indicating their release from lignin and conversion by colon microbiota. However, the extent of lignin degradation was estimated to be low. No notable suppression of microbial conversions was detected based on the formation of linear short chain fatty acids. In addition, experiments with pure strains of lactobacilli and bifidobacteria showed no inhibition of growth by a lignin-rich fraction. Association of lignin with carbohydrates or proteinaceous material may have reduced the possible antimicrobial effects of lignin. The results of the present study provide new information on the significance of lignin as part of dietary fibre indicating its partial metabolism by colon microbiota.",
keywords = "brewer's spent grain, enzymatic fractionation, lignin, colon microbiota, colon metabolic model",
author = "Piritta Niemi",
note = "BA3144 PGN: 86 p. + app. 48 p.",
year = "2016",
language = "English",
isbn = "978-952-60-6699-8",
series = "VTT Science",
publisher = "Aalto University",
number = "124",
address = "Finland",
school = "Aalto University",

}

Panimomäskin entsymaattinen fraktiointi ja ligniinijakeiden mikrobiaineenvaihdunta suolistomallissa : Dissertation. / Niemi, Piritta.

Espoo : Aalto University, 2016. 134 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - Panimomäskin entsymaattinen fraktiointi ja ligniinijakeiden mikrobiaineenvaihdunta suolistomallissa

T2 - Dissertation

AU - Niemi, Piritta

N1 - BA3144 PGN: 86 p. + app. 48 p.

PY - 2016

Y1 - 2016

N2 - The objectives of this thesis were to produce lignin-rich fractions from brewer's spent grain (BSG) and to study the interactions of the lignin in these fractions with colon microbiota in vitro. Different milling pre-treatments were studied to enhance enzymatic hydrolysis of BSG carbohydrates. Ball-milling, which was the most efficient treatment, increased carbohydrate solubilisation from 23 to 45 %. Thus, milling notably improved enzymatic solubility of cell wall polysaccharides but was not effective enough to enable their total hydrolysis. Two lignin-rich fractions (24 and 40 % lignin content) were obtained by enzymatic fractionation of BSG using carbohydrases and proteases. In addition, a separate alkaline extraction provided BSG-derived material with low ferulic acid content. BSG and the fractions were used to study if lignin is degraded and metabolised by colon microbiota in a metabolic model and if lignin suppresses microbial conversions in the colon. A number of mono- and dimeric phenolic metabolites were formed upon digestion of BSG and the fractions by the microbiota. It appeared that many of them were structurally lignin-related indicating their release from lignin and conversion by colon microbiota. However, the extent of lignin degradation was estimated to be low. No notable suppression of microbial conversions was detected based on the formation of linear short chain fatty acids. In addition, experiments with pure strains of lactobacilli and bifidobacteria showed no inhibition of growth by a lignin-rich fraction. Association of lignin with carbohydrates or proteinaceous material may have reduced the possible antimicrobial effects of lignin. The results of the present study provide new information on the significance of lignin as part of dietary fibre indicating its partial metabolism by colon microbiota.

AB - The objectives of this thesis were to produce lignin-rich fractions from brewer's spent grain (BSG) and to study the interactions of the lignin in these fractions with colon microbiota in vitro. Different milling pre-treatments were studied to enhance enzymatic hydrolysis of BSG carbohydrates. Ball-milling, which was the most efficient treatment, increased carbohydrate solubilisation from 23 to 45 %. Thus, milling notably improved enzymatic solubility of cell wall polysaccharides but was not effective enough to enable their total hydrolysis. Two lignin-rich fractions (24 and 40 % lignin content) were obtained by enzymatic fractionation of BSG using carbohydrases and proteases. In addition, a separate alkaline extraction provided BSG-derived material with low ferulic acid content. BSG and the fractions were used to study if lignin is degraded and metabolised by colon microbiota in a metabolic model and if lignin suppresses microbial conversions in the colon. A number of mono- and dimeric phenolic metabolites were formed upon digestion of BSG and the fractions by the microbiota. It appeared that many of them were structurally lignin-related indicating their release from lignin and conversion by colon microbiota. However, the extent of lignin degradation was estimated to be low. No notable suppression of microbial conversions was detected based on the formation of linear short chain fatty acids. In addition, experiments with pure strains of lactobacilli and bifidobacteria showed no inhibition of growth by a lignin-rich fraction. Association of lignin with carbohydrates or proteinaceous material may have reduced the possible antimicrobial effects of lignin. The results of the present study provide new information on the significance of lignin as part of dietary fibre indicating its partial metabolism by colon microbiota.

KW - brewer's spent grain

KW - enzymatic fractionation

KW - lignin

KW - colon microbiota

KW - colon metabolic model

M3 - Dissertation

SN - 978-952-60-6699-8

SN - 978-951-38-8403-1

T3 - VTT Science

PB - Aalto University

CY - Espoo

ER -