ABSTRACT
The red yeast Rhodosporidium toruloides naturally produces microbial lipids and carotenoids. In the past decade or so, many studies demonstrated R. toruloides as a promising platform for ...lipid production owing to its diverse substrate appetites, robust stress resistance and other favorable features. Also, significant progresses have been made in genome sequencing, multi-omic analysis and genome-scale modeling, thus illuminating the molecular basis behind its physiology, metabolism and response to environmental stresses. At the same time, genetic parts and tools are continuously being developed to manipulate this distinctive organism. Engineered R. toruloides strains are emerging for enhanced production of conventional lipids, functional lipids as well as other interesting metabolites. This review updates those progresses and highlights future directions for advanced biotechnological applications.
A review updates research progresses on the red yeast Rhodosporidium toruloidesand highlights future engineering directions.
Sugarcane is one of the major agricultural crops cultivated in tropical climate regions of the world. Each tonne of raw cane production is associated with the generation of 130 kg dry weight of ...bagasse after juice extraction and 250 kg dry weight of cane leaf residue postharvest. The annual world production of sugarcane is ~1.6 billion tones, generating 279 MMT tones of biomass residues (bagasse and cane leaf matter) that would be available for cellulosic ethanol production. Here, we investigated the production of cellulosic ethanol from sugar cane bagasse and sugar cane leaf residue using an alkaline pretreatment: ammonia fiber expansion (AFEX). The AFEX pretreatment improved the accessibility of cellulose and hemicelluloses to enzymes during hydrolysis by breaking down the ester linkages and other lignin carbohydrate complex (LCC) bonds and the sugar produced by this process is found to be highly fermentable. The maximum glucan conversion of AFEX pretreated bagasse and cane leaf residue by cellulases was ~85%. Supplementation with hemicellulases during enzymatic hydrolysis improved the xylan conversion up to 95-98%. Xylanase supplementation also contributed to a marginal improvement in the glucan conversion. AFEX-treated cane leaf residue was found to have a greater enzymatic digestibility compared to AFEX-treated bagasse. Co-fermentation of glucose and xylose, produced from high solid loading (6% glucan) hydrolysis of AFEX-treated bagasse and cane leaf residue, using the recombinant Saccharomyces cerevisiae (424A LNH-ST) produced 34-36 g/L of ethanol with 92% theoretical yield. These results demonstrate that AFEX pretreatment is a viable process for conversion of bagasse and cane leaf residue into cellulosic ethanol. Biotechnol. Bioeng. 2010;107: 441-450.
We investigate the projected sensitivity to effective dark matter (DM)–diboson interaction during the high luminosity
Z
-pole and 240 GeV runs at the proposed Circular Electron Positron Collider ...(CEPC). The proposed runs at the 91.2 GeV
e
+
e
-
center of mass energy offers an interesting opportunity to probe effective dark matter couplings to the
Z
boson, which can be less stringently tested in non-collider searches. We investigate the prospective sensitivity for dimension 6 and dimension 7 effective diboson operators to scalar and fermion dark matter. These diboson operators can generate semi-visible
Z
boson decay, and high missing transverse momentum mono-photon signals that can be test efficiently at the CEPC, with a small and controllable Standard Model
γ
ν
¯
ν
background. Projected sensitivities for the effective
γ
Z
coupling efficient
κ
γ
Z
<
(
1030
GeV
)
-
3
,
(
1970
GeV
)
-
3
for scalar DM,
κ
γ
Z
<
(
360
GeV
)
-
3
,
(
540
GeV
)
-
3
for fermion DM are obtain for 25
fb
-
1
and
2.5
ab
-
1
Z
-pole luminosities assuming the optimal low dark matter mass range. We also compare the CEPC sensitivities to current direct and indirect search limits on these effective DM-diboson operators.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Highlights • We review current biorefinery technologies for producing oil from oleaginous microbes. • We discuss the current bottlenecks impeding economic production of SCO. • We propose strategies ...and methods to surmount the economic bottlenecks.
Yarrowia lipolytica
strain is a promising cell factory for the conversion of lignocellulose to biofuels and bioproducts. Despite the inherent robustness of this strain, further improvements to ...lignocellulose-derived inhibitors toxicity tolerance of
Y. lipolytica
are also required to achieve industrial application. Here, adaptive laboratory evolution was employed with increasing concentrations of ferulic acid. The adaptive laboratory evolution experiments led to evolve
Y. lipolytica
strain yl-XYL + *FA*4 with increased tolerance to ferulic acid as compared to the parental strain. Specifically, the evolved strain could tolerate 1.5 g/L ferulic acid, whereas 0.5 g/L ferulic acid could cause about 90% lethality of the parental strain. Transcriptome analysis of the evolved strain revealed several targets underlying toxicity tolerance enhancements. YALI0_E25201g, YALI0_F05984g, YALI0_B18854g, and YALI0_F16731g were among the highest upregulated genes, and the beneficial contributions of these genes were verified via reverse engineering. Recombinant strains with overexpressing each of these four genes obtained enhanced tolerance to ferulic acid as compared to the control strain. Fortunately, recombinant strains with overexpression of YALI0_E25201g, YALI0_B18854g, and YALI0_F16731g individually also obtained enhanced tolerance to vanillic acid. Overall, this work demonstrated a whole strain improvement cycle by “non-rational” metabolic engineering and presented new targets to modify
Y. lipolytica
for microbial lignocellulose valorization.
Key points
•
Adaptive evolution improved the ferulic acid tolerance of Yarrowia lipolytica
•
Transcriptome sequence was applied to analyze the ferulic acid tolerate strain
•
Three genes were demonstrated for both ferulic acid and vanillic acid tolerance
Rhamnolipids have extensive potential applications and are the most promising biosurfactants for commercialization. The efficient and accurate identification and analysis of these are important to ...their production, application and commercialization. Accordingly, significant efforts have been made to identify and analyse rhamnolipids during screening of producing strains, fermentation and application processes. Cationic cetyltrimethylammonium bromide–methylene blue (CTAB-MB) test combines a series of indirect assays to efficiently assist in the primary screening of rhamnolipids-producing strains, while the secretion of rhamnolipids by these strains can be identified through TLC, FTIR, NMR, electrospray ionization mass spectrometry (ESI-MS) and HPLC-MS analysis. Rhamnolipids can be quantified by colorimetric methods requiring the use of concentrated acid, and this approach has the advantages of reliability, simplicity, low-cost and excellent reproducibility with very low technological requirements. HPLC-MS can also be employed as required as a more accurate quantification method. In addition, HPLC-ELSD has been established as the internationally acceptable measure of rhamnolipids for commercial purposes. The preparation of well-accepted rhamnolipids standards and modifications of analysis operations are essential to further enhance the accuracy and improve the simplicity of rhamnolipid analysis.
Key points
• Current status of R&D works on determination of rhamnolipids is listed
• Advantages and disadvantages of various types analysis are summarized
• Limitations of current rhamnolipid quantification are discussed
Graphical abstract
It is well known that simultaneous saccharification and co-fermentation (SSCF) reduces cellulosic ethanol production cost compared to separate hydrolysis and fermentation (SHF). However, the ...traditional SSCF process of converting Ammonia Fiber Expansion (AFEX) pretreated switchgrass to ethanol using both commercial enzymes and
Saccharomyces cerevisiae 424A(LNH-ST) gave reduced ethanol yield due to lower xylose consumption. To overcome this problem we have developed a two-step SSCF process, in which xylan was hydrolyzed and fermented first followed by the hydrolysis and fermentation of glucan. Important parameters, such as temperature, cellulases loading during xylan hydrolysis and fermentation, initial OD
600 for inoculation of
S. cerevisiae 424A(LNH-ST), and pH, were studied for best performance. Compared with traditional SSCF, the two-step SSCF showed higher xylose consumption and higher ethanol yield. The sugar conversion was also enhanced from 70% by enzymatic hydrolysis to 82% by two-step SSCF. One important finding is that the residue from enzymatic hydrolysis plays a significant role in reducing xylose consumption and ethanol metabolic yield during SSCF.
Summary
Butanol is an important bulk chemical, as well as a promising renewable gasoline substitute, that is commonly produced by solventogenic Clostridia. The main cost of cellulosic butanol ...fermentation is caused by cellulases that are required to saccharify lignocellulose, since solventogenic Clostridia cannot efficiently secrete cellulases. However, cellulolytic Clostridia can natively degrade lignocellulose and produce ethanol, acetate, butyrate and even butanol. Therefore, cellulolytic Clostridia offer an alternative to develop consolidated bioprocessing (CBP), which combines cellulase production, lignocellulose hydrolysis and co‐fermentation of hexose/pentose into butanol in one step. This review focuses on CBP advances for butanol production of cellulolytic Clostridia and various synthetic biotechnologies that drive these advances. Moreover, the efforts to optimize the CBP‐enabling cellulolytic Clostridia chassis are also discussed. These include the development of genetic tools, pentose metabolic engineering and the improvement of butanol tolerance. Designer cellulolytic Clostridia or consortium provide a promising approach and resource to accelerate future CBP for butanol production.
This review focuses on consolidated bioprocessing (CBP) advances for butanol production of cellulolytic Clostridia and various synthetic biotechnologies that drive these advances. Moreover, the efforts to optimize the CBP‐enabling cellulolytic Clostridia chassis are also discussed.
n-Butyl acetate is an important food additive commonly produced via concentrated sulfuric acid catalysis or immobilized lipase catalysis of butanol and acetic acid. Compared with chemical methods, an ...enzymatic approach is more environmentally friendly; however, it incurs a higher cost due to lipase production. In vivo biosynthesis via metabolic engineering offers an alternative to produce n-butyl acetate. This alternative combines substrate production (butanol and acetyl-coenzyme A (acetyl-CoA)), alcohol acyltransferase expression, and esterification reaction in one reactor. The alcohol acyltransferase gene ATF1 from Saccharomyces cerevisiae was introduced into Clostridium beijerinckii NCIMB 8052, enabling it to directly produce n-butyl acetate from glucose without lipase addition. Extractants were compared and adapted to realize glucose fermentation with in situ n-butyl acetate extraction. Finally, 5.57 g/L of butyl acetate was produced from 38.2 g/L of glucose within 48 h, which is 665-fold higher than that reported previously. This demonstrated the potential of such a metabolic approach to produce n-butyl acetate from biomass.
•Post-washing was important to remove inhibition in enzymatic hydrolysis.•Effects of solids loading on monomeric and oligomeric sugar yields were studied.•Enzymatic conversion decrease was mainly due ...to inhibition of glucose and phenolics.
Aqueous ammonia pretreatment was optimized and the limiting factors in high solids enzymatic hydrolysis were assessed. The recommended pretreatment condition to achieve high enzymatic yield was: 180°C, 20% (w/w) ammonia, 30min, and 20% solids content. FT-IR and GC–MS results indicated that most of the lignin was degraded to soluble fragments after pretreatment. The pretreated solids after post-washing showed higher enzymatic digestibility at high solids loading than that without washing. The washed solids required lower cellulase and xylanase dosage than unwashed solids to achieve high sugar yield. Enzymatic conversions were declined with the increased solids loading of pretreated solids, pretreated-washed solids, and filter papers. The results indicated that solids loading in enzymatic hydrolysis was an important factor affecting sugar yield. The increasing concentration of glucose and ligno-phenolics mainly inhibited the enzymatic hydrolysis of aqueous ammonia pretreated corn stover.
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