Abstract:BackgroundExploring different microbial sources for biotechnological production of organic acids is important. Dutch and Thai cow rumen samples were used as inocula to produce organic acid from starch waste in anaerobic reactors. Organic acid production profiles were determined and microbial communities were compared using 16S ribosomal ribonucleic acid gene amplicon pyrosequencing.ResultsIn both reactors, lactate was the main initial product and was associated with growth of Streptococcus spp. (86% average re… Show more
“…1a, and the major bands are assigned in Table 1 [19]. The fingerprint region (1600–1000 cm −1 ) in the spectra of alkali lignin significantly changed after laccase and LMS treatment, corresponding to the stretching vibrations of the different groups in lignin [20]. This suggested that the overall structure of alkali lignin had been destroyed, to some extent, after laccase and LMS pretreatment.…”
Section: Resultsmentioning
confidence: 99%
“…The intensity of the peak at 1267 cm −1 changed slightly after laccase pretreatment, which suggested that the carbonyl in guaiacyl was ruptured during the pretreatment. The signal intensity of alkali lignin at 1633 cm −1 increased after LMS pretreatment, this indicated the formation of small molecule lignin in the LMS pretreatment [20]. Fig.…”
Background
Wheat straw, the most abundant lignocellulosic biomass in China, is rich in cellulose that can be hydrolyzed and then converted into biofuels, such as bioethanol and biohydrogen. However, the accessibility of cellulose and the enzyme activity are greatly reduced in the presence of lignin. This significantly increases the enzyme cost in the saccharification, which hampers industrial production of lignocellulosic biofuels. In this study, a laccase treatment system mediated by 1-hydroxybenzotriazole was employed to modify and degrade lignin to enhance subsequent enzymatic saccharification of wheat straw. A kinetic model considering enzyme adsorption on lignin was proposed to estimate the saccharification performance.
Results
Fourier transform infrared spectroscopy (FTIR) analyses showed that the peak intensity of lignin structure characteristics significantly changed after laccase-mediated system (LMS) treatment. 2D-nuclear magnetic resonance (NMR) analyses indicated that the aromatic ether bonds were cleaved and that guaiacyl (G) was oxidized after LMS treatment. X-ray diffraction (XRD) analyses suggested that the crystallinity of lignocellulose increased due to the partial degradation of lignin. As a result, the nonproductive adsorption of the enzyme on lignin was reduced by 28%, while the reducing sugar yield increased by 26%. A semi-empirical kinetic model was used to estimate the reducing sugar yield, the initial hydrolysis rate (
K
M
) and deactivation rate coefficient (
α
) of LMS-pretreated wheat straw were 0.157 (h
−1
) and 0.214 (h
−1
), respectively. The model showed high accuracy (predicting error < 10%) for describing the behavior of laccase-treated wheat straw hydrolysis when the solid loading is < 5%.
Conclusions
The adsorption ability of the enzyme to lignin was reduced after LMS pretreatment. Physicochemical analyses showed that the chemical groups of lignin and lignocellulose were changed, with the crystallinity of the lignocellulose increasing after LMS treatment. A semi-empirical kinetic model was proposed to estimate the reducing sugar yield, which showed high accuracy for predicting the hydrolysis performance of laccase-treated wheat straw.
“…1a, and the major bands are assigned in Table 1 [19]. The fingerprint region (1600–1000 cm −1 ) in the spectra of alkali lignin significantly changed after laccase and LMS treatment, corresponding to the stretching vibrations of the different groups in lignin [20]. This suggested that the overall structure of alkali lignin had been destroyed, to some extent, after laccase and LMS pretreatment.…”
Section: Resultsmentioning
confidence: 99%
“…The intensity of the peak at 1267 cm −1 changed slightly after laccase pretreatment, which suggested that the carbonyl in guaiacyl was ruptured during the pretreatment. The signal intensity of alkali lignin at 1633 cm −1 increased after LMS pretreatment, this indicated the formation of small molecule lignin in the LMS pretreatment [20]. Fig.…”
Background
Wheat straw, the most abundant lignocellulosic biomass in China, is rich in cellulose that can be hydrolyzed and then converted into biofuels, such as bioethanol and biohydrogen. However, the accessibility of cellulose and the enzyme activity are greatly reduced in the presence of lignin. This significantly increases the enzyme cost in the saccharification, which hampers industrial production of lignocellulosic biofuels. In this study, a laccase treatment system mediated by 1-hydroxybenzotriazole was employed to modify and degrade lignin to enhance subsequent enzymatic saccharification of wheat straw. A kinetic model considering enzyme adsorption on lignin was proposed to estimate the saccharification performance.
Results
Fourier transform infrared spectroscopy (FTIR) analyses showed that the peak intensity of lignin structure characteristics significantly changed after laccase-mediated system (LMS) treatment. 2D-nuclear magnetic resonance (NMR) analyses indicated that the aromatic ether bonds were cleaved and that guaiacyl (G) was oxidized after LMS treatment. X-ray diffraction (XRD) analyses suggested that the crystallinity of lignocellulose increased due to the partial degradation of lignin. As a result, the nonproductive adsorption of the enzyme on lignin was reduced by 28%, while the reducing sugar yield increased by 26%. A semi-empirical kinetic model was used to estimate the reducing sugar yield, the initial hydrolysis rate (
K
M
) and deactivation rate coefficient (
α
) of LMS-pretreated wheat straw were 0.157 (h
−1
) and 0.214 (h
−1
), respectively. The model showed high accuracy (predicting error < 10%) for describing the behavior of laccase-treated wheat straw hydrolysis when the solid loading is < 5%.
Conclusions
The adsorption ability of the enzyme to lignin was reduced after LMS pretreatment. Physicochemical analyses showed that the chemical groups of lignin and lignocellulose were changed, with the crystallinity of the lignocellulose increasing after LMS treatment. A semi-empirical kinetic model was proposed to estimate the reducing sugar yield, which showed high accuracy for predicting the hydrolysis performance of laccase-treated wheat straw.
“…Associations between Pseudoramibacter and ruminant feed efficiency ( Table 3 ) are not well reported in the literature. Pseudoramibacter is a member of the Eubacteriaceae family and can utilize carbohydrates for energy ( Deusch et al, 2017 ), while producing fermentation end products butyrate, acetate, formate, and hydrogen ( Deusch et al, 2017 ; Palakawong Na Ayudthaya et al, 2018 ).…”
Rumen microbiome composition and functionality is linked to animal feed efficiency, particularly for bovine ruminants. To investigate this in sheep, we compared rumen bacterial and archaeal populations (and predicted metabolic processes) of sheep divergent for the feed efficiency trait feed conversion ratio (FCR). In our study 50 Texel cross Scottish Blackface (TXSB) ram lambs were selected from an original cohort of 200 lambs. From these, 26 were further selected for experimentation based on their extreme FCR (High Feed Efficiency, HFE = 13; Low Feed Efficiency, LFE = 13). Animals were fed a 95% concentrate diet
ad libitum
over 36 days. 16S rRNA amplicon sequencing was used to investigate the rumen bacterial and archaeal communities in the liquid and solid rumen fractions of sheep divergent for FCR. Weighted UniFrac distances separated HFE and LFE archaea communities from the liquid rumen fraction (Permanova,
P
< 0.05), with greater variation observed for the LFE cohort (Permdisp,
P
< 0.05). LFE animals exhibited greater Shannon and Simpson diversity indices, which was significant for the liquid rumen fraction (
P
< 0.05).
Methanobrevibacter olleyae
(in liquid and solid fractions) and
Methanobrevibacter millerae
(liquid fraction) were differentially abundant, and increased in the LFE cohort (
P.adj
< 0.05), while
Methanobrevibacter wolinii
(liquid fraction) was increased in the HFE cohort (
P.adj
< 0.05). This suggests that methanogenic archaea may be responsible for a potential loss of energy for the LFE cohort. Bacterial community composition (Permanova,
P >
0.1) and diversity (
P
> 0.1) was not affected by the FCR phenotype. Only the genus
Prevotella 1
was differentially abundant between HFE and LFE cohorts. Although no major compositional shifts of bacterial populations were identified amongst the feed efficient cohorts (
FDR
> 0.05), correlation analysis identified putative drivers of feed efficiency with
Ruminococcaceae UCG-014
(liquid,
rho
= −0.53; solid,
rho
= −0.56) and
Olsenella
(solid,
rho
= −0.40) exhibiting significant negative association with FCR (
P
< 0.05).
Bifidobacterium
and
Megasphaera
showed significant positive correlations with ADG. Major cellulolytic bacteria
Fibrobacter
(liquid,
rho
= 0.43) and
Ruminococcus 1
(liquid,
rho
= 0.41; solid,
rho
= 41) correlated positively with FCR (
P
< 0.05). Our study provides evidence that feed efficiency in sheep is likely influenced by co...
“…was significantly increased under 3 g L -1 COS treatments ( Supplementary Figure S6 ). Members of the phylum Bacteroidetes , including genus Parabacteroides , participated in provisioning the host with energy harvested through the fermentation of indigestible polysaccharides to produce SCFAs ( Johnson et al, 2017 ), and were also related to butyrate production ( Palakawong Na Ayudthaya et al, 2018 ). Moreover, colonic hydrogen concentration in rats was positively correlated with the abundance of genus Parabacteroides ( Nishimura et al, 2018 ).…”
Chitosan oligosaccharides (COS) have shown positive effects on host gut health and influence on intestinal microbial community. However, the bioactivity and mechanism of COS on gut microbiota is still poorly understood. Here, we presented systematic studies of COS on mice fecal/gut microbiota. During in vitro fermentation of COS by mice gut microbiota, total bacterial population significantly decreased after 8-h COS treatment but was returned to the normal level after extended incubation. Consumption of COS and production of SCFAs suggested that COS were utilized by the microbe, although the consumption of chitosan pentasaccharides was obviously slower than others. COS treatments on mice fecal samples caused the decrease of potential pathogenic genera Escherichia/Shigella and the increase of genus Parabacteroides. In vivo animal study indicated that COS reduced population of probiotic genera Lactobacillus, Bifidobacterium and harmful genus Desulfovibrio, and increased abundance of genus Akkermansia. Phylum Proteobacteria was significantly inhibited by COS both in the animal model and in vitro fermentation. Our findings suggested that COS could reform the community structure of gut microbiota. The relationship among COS, gut microbiota and host health deserve further study.
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