Natural Carbon Source Research Articles

Green synthesis of N-doped MWCNTs via simple modification of CVD technique and evaluation of its viability as an electrode in AEMFC

The conventional synthesis of multi-walled carbon nanotubes (MWCNT) presents an environmental challenge due to toxic precursors. This research proposes a green synthesis of MWCNT by chemical vapor deposition (CVD) using a natural carbon source precursor (olive oil). Nitrogen gas was used as an inert atmosphere and a carrier for the evaporator precursor (200 °C). MWCNTs were synthesized at 900 °C using NiCl2 as a catalyst. MWCNTs had two treatments: functionalized and purified with HNO3 and HCl. Different physicochemical techniques characterized the MWCNT, such as X-ray diffraction (XRD), FTIR, high-resolution transmission electron microscopy (HRTEM), XPS, Raman spectroscopy, and CHN-S. The size of the MWCNT grew to be between de 15 a 25 nm with a purity of 20%, while the Raman spectroscopy revealed structural changes in the MWCNT after the purification treatment due to variations in the ID/IG index. All the synthesized MWCNTs were electrochemically characterized with linear sweep and cyclical voltammetry to analyze their electrocatalytic response to oxygen reduction reaction (ORR) in alkaline media.

Catalytic pyrolysis of fatty acids and oils into liquid biofuels and chemicals over supported Ni catalysts on biomass-derived carbon

Herein, biomass-derived activated carbon (bio-AC) was synthesized using rice husk as a biotemplate and natural carbon source. After immobilization of Ni, the supported Ni/bio-AC showed excellent catalytic activity in the pyrolysis of fatty acids to paraffin-based biodiesel in H2-free and solvent-free conditions, corresponding to the conversion of 99.6% and a total alkane yield of 95.1%, including 88.9% heptadecane. Based on comprehensive characterizations, the calculated turnover frequency of Ni/bio-AC was 3.9 times that of conventional Ni/AC. Significantly enhanced olefin selectivity was further obtained by N-doping of Ni/bio-AC, which was attributed to the inhibition of -COO* dissociation by the Ni-N sites. The possible catalytic reaction pathways from stearic acid to heptadecane via aliphatic alcohol as a reaction intermediate were investigated. Besides, efficient conversions of saturated and unsaturated plant oils were also achieved over Ni/bio-NAC catalysts in Py-GC/MS through pulsed catalytic pyrolysis manner, showing a promising prospect for sustainable biofuels and chemical production.

Mg-assisted reduced graphene oxide fabrication under microwave irradiation of a natural source of carbon

Chemical reduction of graphene oxide to form reduced graphene oxide (rGO) is a long process that needs time and energy. In this work, we present a facile one-step method to produce rGO using a domestic microwave oven for 2 min. The chemical composition is studied by X-Ray Photoelectron Spectroscopy (XPS), Raman and X-Ray diffraction (XRD) that confirm the formation of rGO. They reveal also the benifit effect of MgCl2 addition towards the rGO formation. Different amounts of MgCl2 are added to polyethylene glycol (PEG) and a natural source of carbon (glucose) is used to form rGO. The rGO yield is successfully enhanced by addition of MgCl2 low concentration. The oxygen concentration decreases with Mg addition which means that Mg atoms replaced oxygen or simply adsorbed at the edge sites. Moreover, carbon concentration increases with MgCl2 addition, which means that Mg acts as an activator of rGO formation. At high MgCl2 concentration, Mg(OH)2-rGO is formed and has a lot of applications.

Isolation of an Acidophilic Cellulolytic Bacterial Strain and Its Cellulase Production Characteristics

The aim of the study was to isolate and identify a highly efficient cellulolytic bacteria strain that can be used in acidic environments, and then investigate its cellulase production characteristics for the effective utilization of agricultural waste. For this purpose, we set a series of isolation and screening steps, 21 strains were isolated from soil, and an acidophilic strain labeled as B13-2 with high cellulase production was screened using the Gram’ iodine method and cellulase activity assay; it was identified as Raoultella terrigena. Lastly, the culture conditions such as incubation time, incubation temperature, pH, carbon sources, nitrogen sources, and inoculum size were optimized via single-factor experiments, and on this basis, the cellulase production of strain B13-2 was optimized using response surface methodology with cellulase activity as the optimization goal. The results of the response surface optimization showed that the optimum incubation time is 3.1 days, the optimum temperature is 29.9 °C, the optimum pH is 4.1, and the optimum inoculum size is 1.50%, the cellulase activity reached a maximum of 13.503 U/mL, which was about 140% higher than that before optimization. In particular, strain B13-2 had higher cellulase production when rice straws were used as the natural carbon source. Meanwhile, the SEM pictures demonstrated that the surface of the substrate rice straws in an acidic buffer with strain B13-2 was uneven, with larger holes than in the neutral buffer after incubation. It further proved that this strain has a stronger ability to degrade cellulose under acidic conditions. The B13-2 is a kind of acidophilic cellulolytic bacteria. Therefore, it has the potential to be developed into a silage additive agent and provides a high-quality strain resource for the high-value biotransformation of agricultural waste and lays a certain foundation for the sustainable development of agricultural cultivation.

Environmentally friendly g-C3N4/carbon quantum dots nanocomposites as fluorescent and anti-spoofing inks

The major goal of this research is to examine fluorescence (FL) features and application of graphitic carbon nitride/carbon quantum dots (GCN/CQD) nanocomposites as invisible and anti-spoofing inks. GCN/CQD nanocomposites were used for an environmentally friendly synthesis method. To achieve this, starch and urea were, respectively, applied as a natural source of carbon and a nitrogen resource. The mixtures of starch and urea with a weight ratio of 1:5 and 1:10 were synthesized using a two-step pyrolysis and microwave-assisted method. FL behavior of the GCN/CQD aqueous colloids indicated that a change in the urea concentration could result in FL emission in the various areas of visible light. FL emission spectra of the synthesized sample with low amount urea and in the sample including extra urea were, respectively, observed at blue and green regions. Anti-spoofing function of these nanocomposites as inks were confirmed via optical spectroscopy testing and digital photos taken from UV cabinet. The photos and patterns taken from the ink made of GCN/CQD nanocomposites are nearly invisible under daylight but clear and observable open to UV, as a result one could conclude that these are potentially usable in anti-spoofing function of the secure inks.

Pengaruh Pemberian Suspensi Bacillus laterosporus dengan Sumber Karbon Alami Berbeda terhadap Laju Germinasi Kedelai (Glycine max)

The increase in food demand is not in line with the increase in the amount of production and quality of agricultural products. The strategy to increase agricultural production so far has been carried out through the provision of chemical synthetic fertilizers, this strategy has a negative impact on the quality of agricultural land, namely a decrease in the essential organic elements of the soil which are needed by plants. Organic farming is a necessary solution to restore land quality and Bacillus laterosporus is a microorganism that has the ability to produce various beneficial metabolites for plant growth and maintain soil fertility. B. laterosporus is a microorganism that requires a high-quality carbon source to produce high-quality metabolites, so it requires natural carbon sources that are cheap, easy to obtain and not widely used by humans, such as old coconut water, nira and molasses. The aim of the study was to determine the difference in the germination rate of soybeans treated with B. laterosporus suspension with different natural carbon sources so that the best natural carbon source for the growth of B. laterosporus could be identified as an essential component of quality organic fertilizer. Soybean germination rate was measured and observed and compared with the control. The results showed that the provision of natural carbon sources had a good effect on the growth of the number of bacterial cells and the germination rate of soybean seeds.

Spatiotemporal lagging of predictors improves machine learning estimates of atmosphere–forest CO2 exchange

Abstract. Accurate estimates of net ecosystem CO2 exchange (NEE) would improve the understanding of natural carbon sources and sinks and their role in the regulation of global atmospheric carbon. In this work, we use and compare the random forest (RF) and the gradient boosting (GB) machine learning (ML) methods for predicting year-round 6 h NEE over 1996–2018 in a pine-dominated boreal forest in southern Finland and analyze the predictability of NEE. Additionally, aggregation to weekly NEE values was applied to get information about longer term behavior of the method. The meteorological ERA5 reanalysis variables were used as predictors. Spatial and temporal neighborhood (predictor lagging) was used to provide the models more data to learn from, which was found to improve considerably the accuracy of both ML approaches compared to using only the nearest grid cell and time step. Both ML methods can explain temporal variability of NEE in the observational site of this study with meteorological predictors, but the GB method was more accurate. Only minor signs of overfitting could be detected for the GB algorithm when redundant variables were included. The accuracy of the approaches, measured mainly using cross-validated R2 score between the model result and the observed NEE, was high, reaching a best estimate value of 0.92 for GB and 0.88 for RF. In addition to the standard RF approach, we recommend using GB for modeling the CO2 fluxes of the ecosystems due to its potential for better performance.

Green synthesis of N,S-doped carbon dots for tartrazine detection and their antibacterial activities.

A simple, green and low-cost method was developed for the synthesis of highly fluorescent N,S-doped carbon dots (N,S-CDs) via the hydrothermal treatment of Gandha Prasarini (GP) leaves as a natural source of carbon, nitrogen and sulfur. The as-prepared N,S-CDs exhibited excitation-dependent green fluorescence emission (λex = 450 nm, λem = 525 nm) with excellent stability, and were used as a fluorescent probe for the selective detection of tartrazine with a limit of detection of 0.18 μM. The fluorescence quenching of N,S-CDs was due to the inner filter effect. The developed method has been employed for the determination of tartrazine in honey and soft drinks with satisfactory recovery ranging from 92 to 110.2%. In addition, the antibacterial activity of the N,S-CDs was explored against both Gram-negative bacteria, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), and Gram-positive bacteria, Staphylococcus aureus (S. aureus). The antibacterial mechanism of the N,S-CDs was investigated. The results indicated that the antibacterial activity was due to the membrane damage of the bacteria by the N,S-CDs. Besides, the N,S-CDs showed negligible lytic effects on human erythrocytes. These findings will inspire further exploitation of CD-based nano-bactericides in biomedical applications.

A review of synthesis graphene oxide from natural carbon based coconut waste by Hummer’s method

Coconut shell is an agricultural residue usually disposed of through open burning, which has a good potential as an alternative material to synthesize into nanomaterials. The production of carbon from natural sources can overcome the hazardous effect and reduce the risk of pollution. Researchers have developed a method by using coconut shell due to renewable waste product to produce new natural carbon source. This review has focused on research carried out on coconut shell powder (CSP) turn to natural graphite or activated carbon with high carbon content from various region worldwide. Graphene oxide (GO) based on natural graphite coconut shell powder was successfully synthesized with high scale using a modified Hummers method, and the obtained GO was confirmed using X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy, and Raman Spectroscopy.

Nanosensors of Fluorescent Carbon Quantum Dots Derived from Banana Peel: Application in Sr2+ and Co2+ Detection

Natural Carbon Quantum Dots (NCQDs) are known to contain photo luminescence property and stand as a promising nanomaterial group. Therefore, we intended to generate an intelligible and effective hydrothermal procedure for performing the green synthesis of this material through the usage of banana peel waste as a feasible and durable natural carbon source. The obtained NCQDs were characterized by the means of UV-visible absorption spectroscopy, spectrofluorometry, Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD), zeta potential, Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), and Thermo Gravimetric Analysis (TGA). The lack of utilizing any toxic substances has guaranteed the safety of this procedure in all the biological practices. Therefore, the high crystalline and spherical morphology of synthesized NCQDS with an average roughness of about 5.9 nm were indicated by the results of TEM and XRD. We also observed a high water stability and solubility due to the presence of hydroxyl and carboxyl group and excitation- dependent emission performance with the satisfying quantum yield of 12 %. The zeta potential of prepared NCQDs reached up to -27.4 mV. Furthermore, in order to determine the low toxicity and favorable biocompatibility of this product, we studied the toxic effects of NCQDs on the fibroblast cell line of a normal mouse through the MTT assay. In conformity with the gathered data, these NCQDs contain the potential of being utilized as a nontoxic carrier and a fine alternative for bio-sensor, bio-imaging, and drug delivery applications. The development of these NCQDs was completed with the objective of acting as a highly sensitive fluorescent “on-off-on” switch sensor in the course of the selective and simultaneous sensing of Sr2+ and Co2+. Fluorescence data revealed that the binding constants of Sr2+ and Co2+ to NCQDs were to be 1.39 × 104 M-1 and 1.58 × 104 M-1 respectively. The observations were indicative of a linear relationship among the Sr2+ and Co2+ ions volume and the fluorescence intensity throughout the range of 0 to 0.1 mM.

Sustainable carbon sources for green laser-induced graphene: A perspective on fundamental principles, applications, and challenges

Since the discovery of laser-induced graphene (LIG), significant advances have been made to obtain green LIG (gLIG) from abundant, eco-friendly, natural, and organic renewable bio-based carbon sources. Recently, some sustainable and cost-effective electronic devices have been designed with gLIG, resulting in diverse solutions to the environmental impact caused by electronic waste (e-waste). However, there are still several challenges that must be addressed regarding the widespread market implementation of gLIG-based products, from synthesis to practical applications. In this review, we focus on sustainable precursor sources, their conversion mechanisms, physical and chemical properties and applications, along with the challenges related to its implementation, showing the future opportunities and perspectives related to this promising new material. Various systems based on gLIG for energy storage, electrocatalysis, water treatment, and sensors have been reported in the literature. Additionally, gLIG has been proposed for ink formulation or incorporation into polymer matrices, to further expand its use to non-carbon-based substrates or applications for which pristine LIG cannot be directly used. In this way, it is possible to apply gLIG on diverse substrates, aiming at emerging wearable and edible electronics. Thus, this review will bring an overview of gLIG developments, in accordance with the European Green Deal, the United Nations Sustainable Development Goals and the new era of internet-of-things, which demands cost-effective electronic components based on the principles of energy efficiency and sustainable production methods.

Biyokütlelerden Karbon Bazlı Nanomalzemelerin Sentezi Üzerine Kısa Bir Bakış

Biomass from agricultural waste offers an abundant, natural and affordable carbon source for the synthesis of value-added carbonaceous materials. The conversion of these agricultural wastes into nanoscale products relies on the development of environmentally friendly, affordable, simple and scalable new synthesis methods for commercial production of graphene-type nanomaterials. However, all agricultural waste acts as a carbonaceous product required for GO production. Based on this, in this study, new biomass materials and economical approaches were proposed to prepare GO. In addition, the advantages and disadvantages of graphene synthesis methods were discussed and green nanotechnology was examined. Some studies on the synthesis of carbon-based nanomaterials from biomass were examined and the place of graphene in health applications was investigated. How lignocellulosic biomass was converted into carbon-based nanomaterials was investigated and its mechanism was discussed.

Research progress in visualization sensors based on carbon dots

<p indent="0mm">Optical sensors have attracted the attention of many scientists because of their excellent selectivity, sensitivity, stability and low-cost. Carbon dots (CDs) are synthesized by a large number of natural and artificial carbon source materials through a variety of methods, and they can be chemically tuned by doping to achieve the required sensing characteristics. Many visualization sensors based on CDs have been reported, which can be used to detect various ions and molecules with high selectivity and sensitivity, and provides a theoretical basis for the field rapid detection equipment. This article summarizes the sensing mechanism and application of some excellent carbon dots as visualization sensors, and discusses their application potential in the field of public safety analysis.

Saccharide-originated fluorescent carbon dots synthesized by in-liquid plasma with controlled orderliness of carbon core through precursor alteration for selective and rapid metal ion detection

Carbon dots (CDs) have grown interested in replacing metal-based quantum dots due to their fluorescent properties with low toxicity. The green synthesis, therefore, represents a contribution to this research field. Here, we demonstrate the synthesis of CDs from simple saccharides, including fructose, glucose, and sucrose, using an eco-friendly method—solution plasma (SP)—by applying plasma in the aqueous solution of the precursor. Variations and characterizations are conducted to understand the role or influence of each synthesis parameter, i.e. saccharide precursor's molecular structure, solution pH (2, 5, and 8), and post-treatment method (freeze-drying and heat-drying), in the materials' structure and fluorescent properties. Blue light-emitting CDs are prepared from all precursors of pH 5 and 8 through SP, followed by heat-drying. Results show that SP is responsible for the carbon core formation, and thus the precursor type affects the carbon core's orderliness. Heat-drying causes oxidation on the CDs' surface, whereby OH functional groups change to C=O. Among all samples, the CDs synthesized from fructose at pH 5 (Fru-CDs-5) perform the best photoluminescence property, having the highest quantum yield (QY) of 9.16% and exhibiting an outstanding ability to detect Fe 3+ ions. This is the first attempt to evince the potential use of SP to synthesize CDs from natural carbon sources and obtain CDs exhibiting superior fluorescence properties without any doping and complex synthesis steps. In addition to offering a new synthetic approach, this work specifies the role of the SP and the effect of the saccharide's molecular structure, which is the most relevant synthesis parameters mandatory to obtain tailored CDs with precise control. • Carbon dots (CDs) are synthesized from fructose, glucose, and sucrose using the ‘solution plasma (SP)’ process. • This is the first attempt to use SP to synthesize CDs from natural carbon sources. • The role of the SP and the post-treatment method and the effect of the precursor's molecular structure are explored. • The obtained CDs display outstanding sensitivity and selectivity toward Fe 3+ ion detection.

An environment-benign approach of bamboo pulp bleaching using extracellular xylanase of strain Bacillus stratosphericus EB-11 isolated from elephant dung.

The use of microbial enzymes is highly encouraged in paper and pulp industries to reduce the excessive use of hazardous chemicals. During the study, xylanase of BacillusstratosphericusEB-11 was characterized for pulp bleaching applications. The extracellular xylanase was produced under submerged fermentation using bamboo wasteas a natural carbon source. There was fast cell division and enzyme production under optimized fermentation conditions in the bioreactor. The highest activity was 91,200Uafter30h of growth with Km and Vmax of 3.52mg/mL and 391.5μmol/min per mgrespectively. The purified enzyme with molecular mass ~ 60kDa had conferred positive activity on native PAGE. The strong inhibition by ethylenediaminetetraacetate and SDS showed the metallo-xylanase nature of the purified enzyme.The bacterial xylanase reduces the use of hydrogen peroxide by 0.4%. Similarly, biological oxygen demand and chemical oxygen demand were reduced by 42.6 and 35.2%. The xylanase-hydrogen peroxide combined treatment and conventional chlorine dioxide-alkaline (CDE1D1D2) bleaching showed almost similar improvement in physicochemical properties of bamboo pulp. Xylanase-peroxide bleaching reduces the lignin content to 4.95% from 13.32% unbleached pulp. This content after CDE1D1D2treatment was 4.21%. The kappa number decreased from 15.2 to 9.46 with increasing the burst factor (15.51),crystallinity index (60.25%), viscosity (20.1 cp), and brightness (65.4%). The overall finding will encourage the development of new cleaner methods of bleaching in the paper and pulp industry.

A bioconfined synthesis strategy of Sb2S3@N–doped carbon ribbons for boosting ultralong–life sodium storage

Reducing the synthesis costs of electrode materials and improving their electrochemical performance remain key issues regarding the application of sodium–ion batteries (SIBs) in large–scale energy storage devices. Antimony sulfide (Sb2S3) is a promising anode material for SIBs because of its high theoretical capacity. However, its poor electrical conductivity and volume expansion hinder its practical application. Aspergillus niger is an environmentally friendly, low–cost, and renewable fungus with a one–dimensional (1D) structure, it has high application value as a natural carbon source in energy storage materials. Herein, Sb2S3 composite N–doped carbon ribbons (Sb2S3@NCRs) are prepared using Aspergillus niger via the gas–phase sulfuration method. These Sb2S3@NCRs show excellent electrochemical performance as anode materials for SIBs. Using Na3V2(PO4)3 (NVP) as the counter electrode, here Sb2S3@NCRs//NVP is show to maintain a reversible specific capacity of 208 mAh·g−1 at 0.2 A g−1 after 100 cycles. In addition, the step–wise transformation and alloying reactions of Sb2S3@NCRs were verify using in situ X–ray diffraction (XRD) tests. This simple and inexpensive synthesis method provides a new strategy for creating other low–cost large–scale energy storage materials.

Photocatalytic Activity of Zero-Valent Iron Nanoparticles Highly Dispersed on Porous Carbon Materials

During the traditional homogeneous Fenton reaction process for water treatment, the consumption rate constant of Fe2+ is much greater than its regeneration rate constant, which makes Fe2+ an almost stoichiometric loss and produces iron sludge waste. In this article, highly dispersed zero-valent Fe nanoparticles loaded on porous carbon materials (Fe-EMC) were synthesized by a one-step calcination method using Flammulina velutipes natural carbon source and Fe(NO3)3 as raw materials to solve the aforementioned problem. The as-prepared Fe-EMC materials are characterized by X-ray diffraction analysis, scanning electron microscopy, electron probe microanalyzer, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption–desorption measurements. It exhibits excellent photocatalytic activity for the degradation of methylene blue (MB) dyes under a broad pH region. Under conditions of 0.3 g/L Fe-EMC, 0.2 M/L H2O2, pH 7.0–11.0, and 50 mg/L MB, 97.98% of the MB dyes in the solution were completely degraded within 1 h. It was attributed to the efficient regeneration cycle between Fe2+ and Fe3+ in the Fenton-like system with light irradiation, which can promote the generation of active oxygen species.

Emerging applications of sludge biochar-based catalysts for environmental remediation and energy storage: A review

The discovery of carbon-based catalysts triggers a wealth of research towards metal-free catalysis. Various low-cost and earth-abundant biomaterials have been investigated to produce carbonaceous catalysts as they are a natural source of carbon and other functional elements. In recent years, sludge biochar as a catalyst has received considerable research interest because of its promising performance in advanced oxidation processes (AOPs) and energy storage devices (ESDs). Besides, it offers a cost-effective and environmentally friendly sludge valorization method that develops environmental processes based on circular economic principles. In this review, we systematically summarized the state-of-the-art nature of this technology, including catalysts synthesis routes, physicochemical properties , and applications in AOPs and ESDs. A relationship between carbonization factors and the development of catalytically active sites is presented with an in-depth discussion. The advantages and disadvantages of different modification processes are highlighted. In addition, scientific insight is given into various catalytic mechanisms during their applications. Eventually, we have outlined the challenges and prospects of this emerging field. Along with covering the advances in this research, this review comprehensively documented the sludge biochar application in ESDs for the first time. • The innate composition of sludge is beneficial for catalyst preparation. • Sludge biochar engineering renders ultra-high surface area and rich active sites. • Optimized sludge biochar performs promising catalysis reactions in AOPs and ESDs. • Catalytic mechanisms and active sites' roles are elucidated. • Challenges in SB-based catalysis can be overcome, and it has a bright future.

Denitrification Performance in Packed-Bed Reactors Using Novel Carbon-Sulfur-Based Composite Filters for Treatment of Synthetic Wastewater and Anaerobic Ammonia Oxidation Effluent.

To avoid nitrate pollution in water bodies, two low-cost and abundant natural organic carbon sources were added to make up the solid-phase denitrification filters. This study compared four novel solid-phase carbon-sulfur-based composite filters, and their denitrification abilities were investigated in laboratory-scale bioreactors. The filter F4 (mixture of elemental sulfur powder, shell powder, and peanut hull powder with a mass ratio of 6:2.5:1.5) achieved the highest denitrification ability, with an optimal nitrate removal rate (NRR) of 723 ± 14.2 mg NO3–-N⋅L–1⋅d–1 when the hydraulic retention time (HRT) was 1 h. The HRT considerably impacted effluent quality after coupling of anaerobic ammonium oxidation (ANAMMOX) and solid-phase-based mixotrophic denitrification process (SMDP). The concentration of suspended solids (SS) of the ANAMMOX effluent may affect the performance of the coupled system. Autotrophs and heterotrophs were abundant and co-existed in all reactors; over time, the abundance of heterotrophs decreased while that of autotrophs increased. Overall, the SMDP process showed good denitrification performance and reduced the sulfate productivity in effluent compared to the sulfur-based autotrophic denitrification (SAD) process.

Dynamic Control Strategy to Produce Riboflavin with Lignocellulose Hydrolysate in the Thermophile Geobacillus thermoglucosidasius.

Efficient utilization of both glucose and xylose, the two most abundant sugars in biomass hydrolysates, is one of the main objectives of biofermentation with lignocellulosic materials. The utilization of xylose is commonly inhibited by glucose, which is known as glucose catabolite repression (GCR). Here, we report a GCR-based dynamic control (GCR-DC) strategy aiming at better co-utilization of glucose and xylose, by decoupling the cell growth and biosynthesis of riboflavin as a product. Using the thermophilic strain Geobacillus thermoglucosidasius DSM 2542 as a host, we constructed additional riboflavin biosynthetic pathways that were activated by xylose but not glucose. The engineered strains showed a two-stage fermentation process. In the first stage, glucose was preferentially used for cell growth and no production of riboflavin was observed, while in the second stage where glucose was nearly depleted, xylose was effectively utilized for riboflavin biosynthesis. Using corn cob hydrolysate as a carbon source, the optimized riboflavin yields of strains DSM2542-DCall-MSS (full pathway dynamic control strategy) and DSM2542-DCrib (single-module dynamic control strategy) were 5.3- and 2.3-fold higher than that of the control strain DSM 2542 Rib-Gtg constitutively producing riboflavin, respectively. This GCR-DC strategy should also be applicable to the construction of cell factories that can efficiently use natural carbon sources with multiple sugar components for the production of high-value chemicals in future.