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•Cellulose nanofiber (CNF) sheets from all parts of oil palm was obtained.•The mechanical properties of CNF sheet from trunk had advantages over others.•The crystallinity of CNF ...sheets from mesocarp and PKS were lower than trunk and EFB.
Cellulose nanofibers (CNFs) were obtained from three types of oil palm wastes, mesocarp, empty fruit bunch (EFB), and palm kernel shell (PKS), as well as the trunk of the oil palm tree, to compare their morphological, thermal, and mechanical properties. Despite large differences in the chemical components of cell walls in the raw materials, the production of CNFs from all parts of the oil palm were achieved in this work. The morphology and mechanical properties of the CNF sheets obtained from the trunk had advantages over the CNF sheets from wastes, while the thermal degradation properties showed no advantage. Cellulose crystallinity of the CNF sheet from the mesocarp and PKS had lower crystallinity (69.1 and 71.1%), and the highest crystallinity of 77.0% was exhibited by the sheet from the trunk. The value of specific tensile strength and specific Young’s modulus were highest in the CNF sheet of the trunk, and lowest mechanical properties shown in the CNF sheet from the mesocarp. These results strongly suggested that the CNF could be obtained from all parts of the plants, but their properties may vary.
Cellulomonas fimi, Cellulomonas biazotea, and Cellulomonas flavigena are cellulose-degrading microorganisms chosen to compare the degradation of cellulose. C. fimi degraded 2.5 g/L of cellulose ...within 4 days, which was the highest quantity among the three microorganisms. The electric current generation by the microbial fuel cell (MFC) using the cellulose-containing medium with C. fimi was measured over 7 days. The medium in the MFC was sampled every 24 h to quantify the degradation of cellulose, and the results showed that the electric current increased with the degradation of cellulose. The maximum electric power generated by the MFC was 38.7 mW/m2, and this numeric value was 63% of the electric power generated by an MFC with Shewanella oneidensis MR-1, a well-known current-generating microorganism. Our results showed that C. fimi was an excellent candidate to produce the electric current from cellulose via MFCs.
In this paper, we presented a novel microbial fuel cell (bMFC) structure, with a bipolar membrane separating the anode and cathode chambers. A bipolar membrane divides the bMFC into anode and cathode ...chambers. The bipolar membrane comprises anion and cation exchange layers. The anode chamber side has the cation exchange layer, while the cathode chamber side has the anion exchange layer. The anode chamber of the bMFC was loaded with Shewanella oneidensis MR-1 and lactic acid, while the cathode chamber was loaded with pure water and iron (III) hydroxide. The bMFC generated electrons for 20 days at a maximum current density of 30 mA/m2 and the ohmic resistance value was estimated to be 500 Ω. During the operation of the bMFC, both the anode and cathode chambers kept anaerobic conditions. There was no platinum catalyst in the cathode chamber, which is required for the reaction of protons with oxygen. Therefore, oxygen could not serve as an electron acceptor in the bMFC. We considered a bMFC mechanism in which protons produced by S. oneidensis react with hydroxide ions, the counter anions of Fe3+, inside the bipolar membrane to produce water. In other words, the electron acceptor in bMFC would be Fe3+.
Diols are versatile chemicals used for multiple manufacturing products. In some previous studies,
Escherichia coli
has been engineered to produce 1,2-propanediol (1,2-PDO) and 1,3-propanediol ...(1,3-PDO) from glucose. However, there are no reports on the direct production of these diols from starch instead of glucose as a substrate. In this study, we directly produced 1,2-PDO and 1,3-PDO from starch using
E. coli
engineered for expressing a heterologous α-amylase, along with the expression of 1,2-PDO and 1,3-PDO synthetic genes. For this, the recombinant plasmids, pVUB3-SBA harboring
amyA
gene for α-amylase production, pSR5 harboring
pct
,
pduP
, and
yahK
genes for 1,2-PDO production, and pSR8 harboring
gpd1-gpp2
,
dhaB123
,
gdrAB
, and
dhaT
genes for 1,3-PDO production, were constructed. Subsequently,
E. coli
BW25113 (
ΔpflA
) and BW25113 strains were transformed with pVUB3-SBA, pSR5, and/or pSR8. Using these transformants, direct production of 1,2-PDO and 1,3-PDO from starch was demonstrated under microaerobic condition. As a result, the maximum production titers of 1,2-PDO and 1,3-PDO from 1% glucose as a sole carbon source were 13 mg/L and 150 mg/L, respectively. The maximum production titers from 1% starch were similar levels (30 mg/L 1,2-PDO and 120 mg/L 1,3-PDO). These data indicate that starch can be an alternative carbon source for the production of 1,2-PDO and 1,3-PDO in engineered
E. coli
. This technology could simplify the upstream process of diol bioproduction.
Escherichia coli JM109 (pGV3-SBA) can assimilate starch by fusing the starch-digesting enzyme α-amylase from Streptococcus bovis NRIC1535 to an OprI′ lipoprotein anchor on the cell membrane. This ...study shows microbial fuel cells (MFCs) development using this recombinant type of E. coli and starch as fuel. We observed the current generation of MFCs with E. coli JM109 (pGV3-SBA) for 120 h. During this period, it consumed 7.1 g/L of starch. A mediator in the form of anthraquinone-2,6-disulfonic acid disodium salt at 0.2, 0.4, and 0.8 mM was added to the MFCs. The highest maximum-current density (271 mA/m2) and maximum-power density (29.3 mW/m2) performances occurred in the 0.4 mM mediator solution. Coulomb yields were calculated as 3.4%, 3.0%, and 3.5% in 1.0, 5.0, and 10.0 g/L of initial starch, respectively. The concentrations of acetic acid, succinic acid, fumaric acid, and ethanol as metabolites were determined. In particular, 38.3 mM of ethanol was produced from 7.1 g/L of starch. This study suggests the use of recombinant E. coli which can assimilate starch present in starch-fueled MFCs. Moreover, it proposes the possibility of gene recombination technology for using wide variety of biomass as fuel and improving MFC's performance.
The strain of Cellulomonas fimi NBRC 15513 can generate electricity with cellulose as fuel without mediator using a single chamber type microbial fuel cell (MFC) which had 100 mL of chamber and ...50 cm2 of the air cathode. The MFCs were operated over five days and showed the maximum current density of 10.0 ± 1.8 mA/m2, the maximum power density of 0.74 ± 0.07 mW/m2 and the ohmic resistance of 6.9 kΩ. According to the results of cyclic voltammetry, the appearance of the oxidation or reduction peak was not observed from the cell removed solution. The fact is that C. fimi does not secrete mediator-like compounds, while the oxidation peak was observed at +0.68 V from the phosphate buffer containing the washed cell. The peak appearance was caused by the electron transfer activity of which corresponds to cytochrome c, and disappeared after adding antimycin A which inhibits the electron transfer activity. The cell was alive throughout the experiment as the result of a colony forming unit on Luria–Bertani agar plates. This was thought that cytochrome c was on the membrane surface of the living cell and played a role in the direct electron transfer between the cells and anode.
Here we report a novel structure-based microbial screening method for vinyl compound discovery, DISCOVER (direct screening method based on coupling reactions for vinyl compound producers). Through a ...two-step screening procedure based on selective coupling reactions of terminal alkenes, the thiol-ene reaction (1
step of screening) and Mizoroki-Heck reaction, followed by iodine test (2
step of screening), microbes producing vinyl compounds like itaconic acid (IA) can be isolated from soil samples. In the 1
step of screening, soil sources are plated on agar medium supplemented with an antimicrobial agent, α-thioglycerol (TG), and a radical initiator, VA-044 (VA). In the 2
step of screening, vinyl compounds produced in the cultures are labelled with iodobenzene via the Mizoroki-Heck reaction, followed by an iodine test, leading to the detection and characterisation of labelled products. We evaluated the validity of DISCOVER using IA and its producer Aspergillus terreus. Experimental data supported our hypothesis that IA reacts with TG in the medium via the thiol-ene reaction and consequently, A. terreus rapidly forms colonies on the agar medium because of the loss of the antimicrobial activity of TG. Using DISCOVER, high throughput and selective isolation of A. terreus strains producing IA was possible from soils.
The present study demonstrates continuous production of d-lactic acid from cellobiose in a cell recycle fermentation with a hollow fiber membrane using recombinant Escherichia coli constructed by ...deleting its pyruvate formate-lyase activating enzyme gene pflA and expressing a heterologous β-glucosidase on its cell surface. The β-glucosidase gene bglC from Thermobifida fusca YX was cloned into a cell surface display vector pGV3, resulting in pGV3-bglC. Recombinant E. coli JM109 harboring the pGV3-bglC showed β-glucosidase activity (18.9 ± 5.7 U/OD600), indicating the cell surface functioning of mutant β-glucosidase. pH-stat cultivation using d-lactic acid producer E. coli BW25113 (ΔpflA) harboring pGV3-bglC in minimum medium with 10 g/L cellobiose in a jar fermentor under anaerobic condition resulted in 5.2 ± 0.1 g/L of d-lactic acid was obtained after 84 h cultivation, indicating that the engineered E. coli produced d-lactic acid directly from cellobiose. For continuous d-lactic acid production, cell recycle fermentation was conducted under anaerobic condition and the culture was continuously ultrafiltrated with a hollow fiber cartridge. The permeate was drawn to the reservoir and a minimum medium containing 10 g/L cellobiose was fed to the fermentor at the same rate (dilution rate, 0.05 h−1). Thus, this system maintained the d-lactic acid production (4.3–5.0 g/L), d-lactic acid production rate (0.22–0.25 g/L/h), and showed no residual cellobiose in the culture during 72 h operation. Interestingly, the d-lactic acid production rate in cell recycle fermentation was more than 3 times higher than that in the batch operation (0.06 ± 0.00 g/L/h).
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