•Proof of concept of growth on wheat bran for four microorganisms.•Selection of plant biomass-consuming microorganisms can be performed using carbohydrates and proteases specific ...databases.•Degradation of wheat bran can be followed with Fourier Transform Infra-Red spectroscopy coupled to enzyme activity analysis.•Carotenoids, flexirubin and canthaxanthin can be produced from a cheap and renewable carbon source.
Pigments are compounds with highly diverse structures and wide uses, which production is increasing worldwide. An eco-friendly method of bioproduction is to use the ability of some microorganisms to ferment on renewable carbon sources. Wheat bran (WB) is a cheap and abundant lignocellulosic co-product of low recalcitrance to biological conversion. Microbial candidates with theoretical ability to degrade WB were first preselected using specific databases. The microorganisms were Ashbya gossypii (producing riboflavin), Chitinophaga pinensis (producing flexirubin), Chromobacterium vaccinii (violacein) and Gordonia alkanivorans (carotenoids). Growth was shown for each on minimal salt medium supplemented with WB at 5 g.L−1. Activities of the main enzymes consuming WB were measured, showing leucine amino-peptidase (up to 8.45 IU. mL−1) and β-glucosidase activities (none to 6.44 IU. mL−1). This was coupled to a FTIR (Fourier Transform Infra-Red) study of the WB residues that showed main degradation of the WB protein fraction for C. pinensis, C. vaccinii and G. alkanivorans. Production of the pigments on WB was assessed for all the strains except Ashbya, with values of production reaching up to 1.47 mg.L−1. The polyphasic approach used in this study led to a proof of concept of pigment production from WB as a cheap carbon source.
A bacterial strain, arapr2
, was isolated from agricultural soil sampled in Reims, France. Based on its 16S rRNA gene sequence, the strain was affiliated to the family
and more specifically to the ...genus
. The strain had 98.31 % 16S rRNA gene sequence similarity to its closest relative
CR11
and 98.25 % to
NCCP-246
. Genome relatedness indexes revealed that the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between arapr2
and its closest relative (
CR11
) were 92.97 % and 52.00 %, respectively; for
NCCP-246
, the ANI and dDDH values were 82.46 and 27.6%, respectively. The genomic DNA of strain arapr2
was 6.02 Mbp long, had a DNA G+C content of 40.4 mol% and had 5504 protein-coding genes. The results obtained in this study suggests that strain arapr2
(CIP 111872
=LMG 31848
) represents a new species for which the name
sp. nov. is proposed. Due to the fact that this strain has been isolated using wheat straw as carbon source, this novel bacterial strain represents a promising biotechnological tool for the fractionation of lignocellulosic biomass in the context of biorefinery development.
The microorganisms living on the phyllosphere (the aerial part of the plants) are in contact with the lignocellulosic plant cell wall and might have a lignocellulolytic potential. We isolated a
...Saccharibacillus
strain (
Saccharibacillus
WB17) from wheat bran phyllosphere and its cellulolytic and hemicellulolytic potential was investigated during growth onto wheat bran. Five other type strains from that genus selected from databases were also cultivated onto wheat bran and glucose. Studying the chemical composition of wheat bran residues by FTIR after growth of the six strains showed an important attack of the stretching C-O vibrations assigned to polysaccharides for all the strains, whereas the C = O bond/esterified carboxyl groups were not impacted. The genomic content of the strains showed that they harbored several CAZymes (comprised between 196 and 276) and possessed four of the fifth modules reflecting the presence of a high diversity of enzymes families. Xylanase and amylase activities were the most active enzymes with values reaching more than 4746 ± 1400 mIU/mg protein for the xylanase activity in case of
Saccharibacillus deserti
KCTC 33693
T
and 452 ± 110 mIU/mg protein for the amylase activity of
Saccharibacillus
WB17. The total enzymatic activities obtained was not correlated to the total abundance of CAZyme along that genus. The
Saccharibacillus
strains harbor also some promising proteins in the GH30 and GH109 modules with potential arabinofuranosidase and oxidoreductase activities. Overall, the genus
Saccharibacillus
and more specifically the
Saccharibacillus
WB17 strain represent biological tools of interest for further biotechnological applications.
The enzymatic production of xylo-oligosaccharides (XOs) from destarched wheat bran with a GH11 xylanase was studied. Xylo-oligosaccharides (XOs) produced were separated into different fractions ...according to their degree of polymerization (DP) and the nature of their substituents: arabinoxylo-oligosaccharides (AXOs) with a DP from 2 to 3 and DP from 2 to 6 and feruloylated arabinoxylo-oligosaccharides (FAXOs) esterified by ferulic and p-coumaric acids with a DP from 3 to 6. Both AXOs (short and long DP) and FAXOs stimulated the growth of Bifidobacterium adolescentis, Faecalibacterium prausnitzii, and Prevotella copri similarly but not Lactobacillus rhamnosus. The utilization of AXOs and FAXOs as a carbon source resulted in the increase in turbidity, decrease in pH, and production of short-chain fatty acids (SCFAs) in the culture broth. The highest amount of SCFAs was produced by F. prausnitzii using FAXOs. Results suggest that FAXOs and AXOs have the potential to be considered as prebiotics.
Lignocellulosic biomass is rich in lignins, which represent a bottomless natural source of aromatic compounds. Due to the high chemical complexity of these aromatic polymers, their biological ...fractionation remains challenging for biorefinery. The production of aromatics from the biological valorization of lignins requires the action of ligninolytic peroxidases and laccases produced by fungi and bacteria. Therefore, identification of efficient ligninolytic enzymes with high stability represents a promising route for lignins biorefining. Our strategy consists in exploiting the enzymatic potential of the thermophilic bacterium
Thermobacillus xylanilyticus
to produce robust and thermostable ligninolytic enzymes. In this context, a gene encoding a putative catalase-peroxidase was identified from the bacterial genome. The present work describes the production of the recombinant protein, its biochemical characterization, and ligninolytic potential. Our results show that the catalase-peroxidase from
T. xylanilyticus
is thermostable and exhibits catalase-peroxidase and manganese peroxidase activities. The electrochemical characterization using intermittent pulse amperometry showed the ability of the enzyme to oxidize small aromatic compounds derived from lignins. This promising methodology allows the fast screening of the catalase-peroxidase activity towards small phenolic molecules, suggesting its potential role in lignin transformation.
Key points
• Production and characterization of a new thermostable bacterial catalase-peroxidase
• The enzyme is able to oxidize many phenolic monomers derived from lignins
• Intermittent pulse amperometry is promising to screen ligninolytic enzyme
Graphical abstract
Streptomyces silvae sp. nov., isolated from forest soil Besaury, Ludovic; Martinet, Lucas; Mühle, Estelle ...
International journal of systematic and evolutionary microbiology,
12/2021, Volume:
71, Issue:
12
Journal Article
Peer reviewed
Open access
A bacterial strain, named For3
, was isolated from forest soil sampled in Champenoux, France. Based on its 16S rRNA gene sequence, the strain was affiliated to the family
and, more specifically, to ...the genus
. The strain had 99.93% 16S rRNA gene sequence similarity to its closest relative strains
ATCC 33331
,
ATCC 27416
,
NRRL ISP-5322
and
NRRL B-16504
. The phylogenomic tree using the genome blast distance phylogeny method showed that the closest relative strain was
NRRL ISP-5137
and that For3
represents a new branch among the
. Genome relatedness indexes revealed that the average nucleotide identity and digital DNA-DNA hybridization values between For3
and its closest phylogenomic relative (
NRRL ISP-5137
) were 88.39 and 39.2 %, respectively. The G+C content of the genome was 71.4 mol% and its size was 7.96 Mb with 7492 protein-coding genes. Strain For3
harboured complete metabolic pathways absent in the closest relative strains such as cellulose biosynthesis, glycogen degradation I, glucosylglycerate biosynthesis I. Anteiso-C
, iso-C
, anteiso-C
and MK-9(H4)/MK-9(H6) were the predominant cellular fatty acids and respiratory quinones, respectively. Phenotypic and genomic data supported the assignment of strain For3
to a novel species
sp. nov., within the genus
, for which the type strain is For3
(=CIP 111908
=LMG 32186
).
Purpose
Microbial fermentation on agro-industrial co-products is an interesting strategy for the bioproduction of metabolites of interest, as it lowers the costs of production and uses renewable and ...abundant carbon sources. Violacein is a purple pigment with interesting properties that is commonly produced by fermentation.
Chromobacterium vaccinii
, a wild-type, natural and non-toxic Proteobacteria (Pseudomonadota), has the ability to produce violacein. However, to select an optimal co-product as carbon source, it is necessary to understand its use of the different constituents of plant biomass.
Methods
Growth and violacein production of
C
.
vaccinii
were first studied on the main components of plant biomass. Then, they were assessed in presence of raw co-products at various concentrations. Tryptophan, a precursor of violacein biosynthesis, was added in order to evaluate the impact on violacein production yields.
Results
C
.
vaccinii
was able to grow on gluten (wheat protein), as well as on low concentrations of glucose. Selecting protein-rich substrates such as soybean and rapeseed cakes led to improved growth and violacein bioproduction. Addition of tryptophan led to net increases in violacein, but had low impacts on the bacterial growth.
Conclusion
Understanding microbial growth mechanisms during bioproduction of molecules of interest is key in order to select the best adapted agro-industrial co-products used as substrate. This study allowed to better characterize growth of
C
.
vaccinii
on various carbon sources and plant biomass, and showed that an optimal substrate with the addition of tryptophan could increase greatly the bioproduction yields of violacein by
C
.
vaccinii
.
Graphical abstract
Thermobacillus xylanilyticus
is a thermophilic and hemicellulolytic bacterium of interest for the production of thermostable hemicellulases. Enzymes’ production by this bacterium is challenging, ...because the proliferation of a cheating subpopulation of cells during exponential growth impairs the production of xylanase after serial cultivations. Accordingly, a strategy of successive cultivations with cells transfers in stationary phase and the use of wheat bran and wheat straw as carbon sources were tested. The ratio between subpopulations and their corresponding metabolic activities were studied by flow cytometry and the resulting hemicellulases production (xylanase, acetyl esterase and β-xylosidase) followed. During serial cultivations, the results pointed out an increase of the enzymatic activities. On xylan, compared to the first cultivation, the xylanase activity increases by 7.15-fold after only four cultivations. On the other hand, the debranching activities were increased by 5.88-fold and 57.2-fold on wheat straw and by 2.77-fold and 3.34-fold on wheat bran for β-xylosidase and acetyl esterase, respectively. The different enzymatic activities then stabilized, reached a plateau and further decreased. Study of the stability and reversibility of the enzyme production revealed cell-to-cell heterogeneities in metabolic activities which could be linked to the reversibility of enzymatic activity changes. Thus, the strategy of successive transfers during the stationary phase of growth, combined with the use of complex lignocellulosic substrates as carbon sources, is an efficient strategy to optimize the hemicellulases production by
T. xylanilyticus
, by preventing the selection of
cheaters
.
Abstract
Streptomyces coelicolor A3(2) is considered as the model strain among the Streptomyces and has the capacity to produce several natural molecules. Our hypothesis was that cultivation of the ...strain onto a complex carbon source such as wheat bran (WB) would induce the production of various secondary metabolites due to the presence of complex polysaccharides. A multiapproach has been performed in order to investigate: (1) whether that strain could degrade lignocellulose; (2) which enzymatic and metabolic pathways secondary were over-expressed when grown on WB. The transcriptomic approach showed the expression of several CAZymes significantly expressed when grown on WB such as endoglucanases (encoding for GH74, GH5_8, and GH12) and xylanases (GH11 and CE4 encoding for respectively endo-1,4-beta-xylanase and an acetyl-xylan esterase). Enzymatic activities showed an expression of xylanase (115.3 ± 32.2 mUI/ml) and laccase–peroxidase (101.5 ± 10.9 mUI/ml) during WB degradation by S. coelicolor A3(2). Metabolomics showed that the production of secondary metabolites differed between growth on either glucose or WB as carbon source, which may be correlated to the complexity of carbon compounds within WB, which are similar to the ones encountered in soils and should represent more the in situ carbon conditions which Streptomyces might face off. This opens opportunities for the bioproduction of molecules of interest from WB.
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