Utilization Of Crude Glycerol Research Articles

Simulation and optimization of crude glycerol refining process as a co-product of biodiesel

Glycerol is an essential chemical raw material widely used in industries such as food, pharmaceuticals, cosmetics, tobacco, and textiles. With the increasing production of biodiesel, a considerable amount of crude glycerol co-product is generated. Purification of crude glycerol by separating it from biodiesel co-products can lead to the production of high-purity glycerol, thus enabling the synthesis of high-value-added chemicals to reduce the production cost of biodiesel. This paper proposes a new glycerol purification process based on the acidification of potassium oleate soap using sulphuric acid. The composition of crude glycerol is complex. The presence of salts can affect the binary interaction parameters of glycerol and water. The ion forms resulting from the ionization of potassium fatty acid soaps are not available in the database and require important data to be provided through physical property estimation. Additionally, the dissociation of sulphuric acid is involved in the system. These issues make it challenging to propose a complete process based on the characteristics of crude glycerol. In this study, the vapor–liquid equilibrium data of the glycerol-water system containing potassium sulphate under reduced pressure were experimentally determined, and the binary interaction parameters of the glycerol-water system were regressed and used in the subsequent process simulation. The entire process of crude glycerol refining from biodiesel co-products was simulated and optimized using Aspen Plus software, proposing an optimized complete refining process for crude glycerol and designing a crude glycerol refining process with a production scale of 100,000 tons per year. The potassium oleate soap is first acidified with sulphuric acid, then removed by centrifugation, with the resulting lower layer entering the distillation process. We compared two different distillation processes and identified the more optimal separation sequence. Glycerol products with a mass concentration of 99.2% were obtained, with glycerol and methanol yields of 98.83% and 99.79%, respectively. Based on the above research, energy integration and optimization of the process were further investigated through pinch analysis. Overall, energy savings of 7.192 Gcal/h were achieved, resulting in a reduction in energy consumption of 40.65%. This paper proposes a new purification scheme for crude glycerol and an energy integration scheme to reduce the purification cost of high-purity glycerol. This is significant for the rational utilization of crude glycerol, a co-product of biodiesel.

The effects of crude glycerol addition on biogas production

Crude glycerol is a by-product of biodiesel production in which the number increases every year and is quite an expensive purification process to meet the technical standards required by consumer industries. To overcome this, it is important to find alternatives for crude glycerol utilization to increase the economic feasibility of the biodiesel industry. This study aimed to evaluate the technical feasibility of biogas production with the addition of crude glycerol from a Palm Oil Plant. The glycerol was introduced into 500mL Anaerobic Digester (AD) as a carbon source and energy source for the growth of methanogenic bacteria along with cow dung and Distilled Water with a ratio of 1:1. The addition of crude glycerol was 5% wt (GL5), 10% wt (GL10) dan 15% wt (GL15), and one control reactor without crude glycerol addition (GL0). AD was operated in a batch system at mesophilic conditions for 30 days. The highest biogas yield was obtained in the experimental set GL10 as much as 380 mL/g VS and was formed on the 3rd day but the highest percentage of methane gas (CH4) was obtained from the control set GL0 as much as 60.2%. In addition to the identification of bacteria, it was found that the type of Bacillus sp in the GL10 treatment was the most biogas producer, and based on the results of its bio-slurry analysis it could be used as organic fertilizer and soil improvement for agriculture and degraded soil.

Evaluating oleaginous yeasts for enhanced microbial lipid production using sweetwater as a sustainable feedstock

BackgroundYeasts exhibit promising potential for the microbial conversion of crude glycerol, owing to their versatility in delivering a wide range of value-added products, particularly lipids. Sweetwater, a methanol-free by-product of the fat splitting process, has emerged as a promising alternative feedstock for the microbial utilization of crude glycerol. To further optimize sweetwater utilization, we compared the growth and lipid production capabilities of 21 oleaginous yeast strains under different conditions with various glycerol concentrations, sweetwater types and pH.ResultsWe found that nutrient limitation and the unique carbon composition of sweetwater boosted significant lipid accumulation in several strains, in particular Rhodosporidium toruloides NRRL Y-6987. Subsequently, to decipher the underlying mechanism, the transcriptomic changes of R. toruloides NRRL Y-6987 were further analyzed, indicating potential sugars and oligopeptides in sweetwater supporting growth and lipid accumulation as well as exogenous fatty acid uptake leading to the enhanced lipid accumulation.ConclusionOur comparative study successfully demonstrated sweetwater as a cost-effective feedstock while identifying R. toluroides NRRL Y-6987 as a highly promising microbial oil producer. Furthermore, we also suggested potential sweetwater type and strain engineering targets that could potentially enhance microbial lipid production.Graphical abstract

Kinetic & thermodynamic studies of green fuel additive solketal from crude glycerol over metakaolin clay catalyst

Biodiesel synthesis produces about 10 % glycerol as a byproduct, prompting environmental concerns. The utilization of crude glycerol into valuable products requires an Eco-friendly technique. This study depicts glycerol acetalization using acetone and novel catalyst acid-treated metakaolin clay. Raw kaolin clay was calcined at 600 °C and treated with acid at 102 °C for 3 h. Afterward, acid activated clay was filtrate and dried in oven to remove moisture content. The catalyst prepared with a 5 M solution of sulfuric acid exhibited the highest surface area of 82.33 m2. g−1 and gave the highest yield (80 %) of Solketal with 73 % of glycerol conversion under optimum conditions. The ketalization reaction of Solketal synthesis was studied in terms of thermodynamics and kinetics. A Langmuir-Hinshelwood rate expression based on two-parameter kinetic law was used in this study. From the kinetic studies, activation energies (EA) of forward and backward reactions were found to be K1 = 39.23 kJ. mol−1 and K2 = 35.70 kJ. mol−1 respectively. Furthermore, reaction was exothermic having an enthalpy of ΔHo = −18.86 kJ. mol−1 and the entropy ΔSo = −0.1 kJ. mol−1 calculated from this process. Solketal derived from sustainable sources such as bio-glycerol and biomass-based acetone, has a wide range of uses as fuel additives and medicines industry. This research marks a significant advancement in the development of a continuous synthesis technique for Solketal and its recovery from glycerol-acetone mixtures.

Vacuum-assisted adsorption of Candida rugosa lipase with nanotubes for monooleoglycerol synthesis

A surplus of crude glycerol has been produced as a by-product due to the escalating production of biofuels. Utilization of crude glycerol for monoolein production which offers a different approach using the abandoned crude glycerol from the biodiesel sector is the main aim of this study. Immobilized lipase was used in this investigation to catalyse the direct esterification of oleic acid and glycerol, which resulted in monoolein. The immobilized Candida rugosa lipase onto the halloysite nanotubes (HNTs) has shown remarkably promising attainment of lipase activity and loading capacity. The immobilised lipase was optimised for crucial parameters (HNT to lipase ratio, pH, temperature, and pressure) via response surface methodology (RSM). The recommended optimum conditions obtained are pH 6, 38.6 °C, and 0.33 atm (81.92% lipase activity). To analyse influences of reaction period, temperature, mixing rate, and crude glycerol to oleic acid molar ratio on the esterification reaction was carried out using the optimized conditions of immobilization process. The optimum conditions for physically immobilised lipase were to yield 88.97% monoolein produced at 42 °C in a substrate ratio of 1:4 (oleic acid: glycerol) stirred at 200 rotations per minute (rpm) with 16 h’ incubation time. Based on the research's findings, it was confirmed that HNT has good application potential for enzyme immobilization carriers.

Novel evolved Yarrowia lipolytica strains for enhanced growth and lipid content under high concentrations of crude glycerol

BackgroundYarrowia lipolytica is a well-studied oleaginous yeast known for its ability to accumulate and store intracellular lipids, while growing on diverse, non-conventional substrates. Amongst them, crude glycerol, a low-cost by-product of the biodiesel industry, appears to be an interesting option for scaling up a sustainable single-cell oil production process. Adaptive laboratory evolution (ALE) is a powerful tool to force metabolic adaptations endowing tolerance to stressful environmental conditions, generating superior phenotypes with industrial relevance.ResultsY. lipolytica MUCL 28849 underwent ALE in a synthetic medium with increasing concentration of pure or crude glycerol as a stressing factor (9–20% v/v) for 520 generations. In one case of pure glycerol, chemical mutagenesis with ethyl methanesulfonate (EMS) was applied prior to ALE. Growth profile, biomass production and lipid content of 660 evolved strains (EVS), revealed 5 superior isolates; exhibiting from 1.9 to 3.6-fold increase of dry biomass and from 1.1 to 1.6-fold increase of lipid concentration compared to the parental strain, when grown in 15% v/v crude glycerol. NGS for differential gene expression analysis, showed induced expression in all EVS affecting nucleosomal structure and regulation of transcription. As strains differentiated, further changes accumulated in membrane transport and protein transport processes. Genes involved in glycerol catabolism and triacylglycerol biosynthesis were overexpressed in two EVS. Mismatches and gaps in the expressed sequences identified altered splicing and mutations in the EVS, with most of them, affecting different components of septin ring formation in the budding process. The selected YLE155 EVS, used for scale-up cultivation in a 3L benchtop bioreactor with 20% v/v crude glycerol, achieved extended exponential phase, twofold increase of dry biomass and lipid yields at 48 h, while citric acid secretion and glycerol consumption rates were 40% and 50% lower, respectively, compared to the parental strain, after 24 h of cultivation.ConclusionALE and EMS-ALE under increasing concentrations of pure or crude glycerol generated novel Y. lipolytica strains with enhanced biomass and lipid content. Differential gene expression analysis and scale-up of YLE155, illustrated the potential of the evolved strains to serve as suitable “chassis” for rational engineering approaches towards both increased lipid accumulation, and production of high-added value compounds, through efficient utilization of crude glycerol.

Enhancing erythritol production from crude glycerol in a wild-type Yarrowia lipolytica by metabolic engineering.

Background: Erythritol is a zero-calorie sweetener that is widely used in the food, pharmaceutical, and medical industries. Crude glycerol is the main by-product of biodiesel, and the effective utilization of crude glycerol will help to improve biodiesel viability. Previous studies on the production of erythritol from Y. lipolytica using crude glycerol as a carbon source have focused on optimizing the fermentation process of the mutant Y. lipolytica Wratislavia K1, while metabolic engineering has not been successfully applied. Results: To this end, we engineered the yeast Y. lipolytica to increase the productivity of this strain. Wild strains tolerant to high concentrations of crude glycerol were screened and identified. A series of rational metabolic approaches were employed to improve erythritol production. Among them, the engineered strain Y-04, obtained by tandem overexpression of GUT1 and GUT2, significantly increased glycerol assimilation by 33.3%, which was consistent with the results of RT-qPCR analysis. The effects of tandem overexpression of GUT1, GUT2, TKL1, and TAL1 on erythritol synthesis were also evaluated. The best results were obtained using a mutant that overexpressed GUT1, GUT2, and TKL1 and knocked out EYD1. The final Y-11 strain produced 150 g/l erythritol in a 5-L bioreactor with a yield and productivity of 0.62 g/g and 1.25 g/l/h, respectively. To the best of our knowledge, this is the highest erythritol yield and productivity from crude glycerol ever reported in Y. lipolytica. Conclusion: This work demonstrated that overexpression of GUT1, GUT2, and TKL1 and knockdown of EYD1 could be used to improve crude glycerol utilization and erythritol synthesis in Y. lipolytica. The process parameters such as erythritol yield and productivity were significantly elevated, which is valuable for industrial applications. Crude glycerol, as a carbon source, could efficiently restrict the synthesis of by-products while enhancing the generation of erythritol, compared to glucose. This indicates considerable potential for synthesizing value-added products from crude glycerol by Y. lipolytica.

A comprehensive review on catalytic etherification of glycerol to value-added products

Abstract The increase in biodiesel production has resulted in the oversupply of glycerol into the market. Purified and processed glycerol has found many direct applications in pharmaceuticals, food, etc. However, the cost of processing and market value of processed glycerol has driven the research of direct utilization of crude glycerol to industrially essential chemicals. Various methods and research have been devoted to using glycerol to produce value-added products separately. Glycerol can undergo several transformation reactions like hydrogenation, oxidation, alcoholysis, and etherification. Etherification of glycerol can be divided into three main reactions: self-etherification, using alcohol, and olefins and these products have vast applications such as fuel additives, plasticizer, etc. The current review presents a comprehensive summary of glycerol etherification to value-added products and their applications. The catalytic system developed along with reaction conditions and the factors responsible for the better activity is also discussed. Overall, the review presents a detailed discussion on the catalytic system developed, the utilization of different alcohols and olefins, and the application of products. Moreover, the environmental and economic aspects of the etherification of glycerol via various conversion routes while assessing the process parameters needs to be tackled to attain wider adoption of the process.

Glycerol steam reforming over hydrothermal synthetic Ni-Ca/attapulgite for green hydrogen generation

• Glycerol steam reforming over hydrothermal synthetic Ni-Ca/ATP was firstly studied. • Effect of Ca content and preparation method on Ni/ATP structure was investigated. • Hydrothermal synthesis ( hs ) enhanced the distribution of Ca and Ni species over ATP. • Ni-6Ca/ATP- hs had strong CO 2 adsorption and abundant Ni-CaO x interfaces. • Ni-6Ca/ATP- hs exhibited superior performance and sinter/coke durability for GSR. Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12%, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni- x Ca/ATP ( x = 3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation ( ci ) and hydrothermal synthesis ( hs ) method and then tested in GSR. Characterization results of XRD, N 2 adsorption–desorption, H 2 -TPR, HRTEM, XPS, and NH 3 /CO 2 -TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO 2 . This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaO x interface sites. Therefore, Ni-6Ca/ATP- hs exhibits the highest conversion (86.77%) of glycerol to gas product and H 2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP- hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

Recovery and utilization of crude glycerol, a biodiesel byproduct.

Biodiesel production has increased significantly in the past decade because it has been demonstrated to be a viable alternative and renewable fuel. Consequently, the production of crude glycerol, the main byproduct of the transesterification of lipids to biodiesel, has risen as well. Therefore, the effective recovery and utilization of crude glycerol can provide biodiesel with additional value. In this review, we first summarized the state-of-the-art progress on crude glycerol recovery and purification. Subsequently, numerous approaches have been reviewed for the utilization of crude glycerol, including use as animal feeds, for combustion, anaerobic fermentation, and chemical conversion. Finally, an extensive discussion and outlook is presented in relation to the techniques and processes in the chemical conversion of crude glycerol.

Bioconversions of Biodiesel-Derived Glycerol into Sugar Alcohols by Newly Isolated Wild-Type Yarrowia lipolytica Strains

The utilization of crude glycerol, generated as a by-product from the biodiesel production process, for the production of high value-added products represents an opportunity to overcome the negative impact of low glycerol prices in the biodiesel industry. In this study, the biochemical behavior of Yarrowia lipolytica strains FMCC Y-74 and FMCC Y-75 was investigated using glycerol as a carbon source. Initially, the effect of pH value (3.0–7.0) was examined to produce polyols, intracellular lipids, and polysaccharides. At low pH values (initial pH 3.0–5.0), significant mannitol production was recorded. The highest mannitol production (19.64 g L−1) was obtained by Y. lipolytica FMCC Y-74 at pH = 3.0. At pH values ranging between 5.0 and 6.0, intracellular polysaccharides synthesis was favored, while polyols production was suppressed. Subsequently, the effect of crude glycerol and its concentration on polyols production was studied. Y. lipolytica FMCC Y-74 showed high tolerance to impurities of crude glycerol. Initial substrate concentrations influence polyols production and distribution with a metabolic shift toward erythritol production being observed when the initial glycerol concentration (Gly0) increased. The highest total polyols production (=56.64 g L−1) was obtained at Gly0 adjusted to ≈120 g L−1. The highest polyols conversion yield (0.59 g g−1) and productivity (4.36 g L−1 d−1) were reached at Gly0 = 80 g L−1. In fed-batch intermittent fermentation with glycerol concentration remaining ≤60 g L−1, the metabolism was shifted toward mannitol biosynthesis, which was the main polyol produced in significant quantities (=36.84 g L−1) with a corresponding conversion yield of 0.51 g g−1.

Repsol to invest EUR 2.5 bn to ramp up renewable hydrogen capacity

Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12 %, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni-xCa/ATP (x=3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation (ci) and hydrothermal synthesis (hs) method and then tested in GSR. Characterization results of XRD, N2 adsorption-desorption, H2-TPR, HRTEM, XPS, and NH3/CO2-TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO2. This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaOx interface sites. Therefore, Ni-6Ca/ATP-hs exhibits the highest conversion (86.77%) of glycerol to gas product and H2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP-hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

BASF builds battery recycling prototype and pilot catalyst units

Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12 %, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni-xCa/ATP (x=3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation (ci) and hydrothermal synthesis (hs) method and then tested in GSR. Characterization results of XRD, N2 adsorption-desorption, H2-TPR, HRTEM, XPS, and NH3/CO2-TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO2. This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaOx interface sites. Therefore, Ni-6Ca/ATP-hs exhibits the highest conversion (86.77%) of glycerol to gas product and H2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP-hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

Evonik is building a new alkoxides plant in Southeast Asia

Glycerol steam reforming (GSR) is one of the promising technologies that can realize renewable hydrogen production and efficient utilization of crude glycerol. To illuminate the functions of Ca content (3%, 6%, 9%, and 12 %, by mass) and preparation method for Ni/ATP catalyst structure and its catalytic behaviors, the Ni-xCa/ATP (x=3%, 6%, 9%, and 12%, by mass) catalysts are prepared by co-impregnation (ci) and hydrothermal synthesis (hs) method and then tested in GSR. Characterization results of XRD, N2 adsorption-desorption, H2-TPR, HRTEM, XPS, and NH3/CO2-TPD demonstrate that the combined effect between appropriate Ca additive (6%, by mass) and hs enhance catalyst reducibility, uniform distribution of Ca additive and nickel species over ATP, and adsorption for CO2. This attributes to hs method protects the ATP framework through suppressing the interaction of Ca with ATP and promotes the formation of Ni-CaOx interface sites. Therefore, Ni-6Ca/ATP-hs exhibits the highest conversion (86.77%) of glycerol to gas product and H2 yield (76.17%) and selectivity (58.56%) during GSR. Furthermore, XRD, HRTEM, TG-DTG and Raman analyses confirm that Ni-6Ca/ATP-hs also reveals outstanding anti-sintering and coke resistance. In addition, the structural evolution process of Ni/ATP catalyst with Ca introduction and hs method is presented. Considering the high performance, simple preparation process and low cost, the as-prepared catalyst providing new opportunities for utilization of glycerol derived from biodiesel industry.

Crude Glycerol as a Potential Feedstock for Future Energy via Thermochemical Conversion Processes: A Review

Biodiesel is an emerging substitute for petroleum-based products. It is considered an ecologically safe and sustainable fuel. The high cost of biodiesel production is linearly related to its feedstock. Crude glycerol, which is a by-product of the biodiesel industry, is also a major challenge that must be addressed. A large volume of crude glycerol needs to be disposed of, and this involves processing, dumping, and land requirements. This increases the cost of biodiesel production. One way to decrease the cost of biodiesel production is to utilize its by-product to make valuable products. Crude glycerol can be processed to produce a variety of chemicals and products. The present utilization of crude glycerol is not enough to bring down its surplus availability. Thermochemical conversion processes can utilize crude glycerol as a starting feedstock and convert it into solid, liquid, and gaseous fuels. The utilization of crude glycerol through integrated thermochemical conversion processes could lead to an integrated biorefinery. This review paper highlights the research scope for areas where crude glycerol could be utilized as a feedstock or co-feedstock in thermochemical conversion technology. Various thermochemical conversion processes, namely, gasification, pyrolysis, combustion, catalytic steam reforming, liquefaction, and supercritical water reforming, are discussed and shown to be highly suitable for the use of crude glycerol as an economical feedstock. It is found that the integration of crude glycerol with other thermochemical conversion processes for energy production is a promising option to overcome the challenges related to biodiesel production costs. Hence, this paper provides all the necessary information on the present utilization status of crude glycerol in thermochemical conversion processes, as well as identifying possible research gaps that could be filled by future research studies.

Efficient Production of Polyhydroxyalkanoate Through Halophilic Bacteria Utilizing Algal Biodiesel Waste Residue.

The objective of the current work was to investigate the potential of halophilic bacterial isolates for efficient utilization of crude glycerol from algal biodiesel waste into polyhydroxyalkanoates (PHAs) a green plastic. Screening of the isolates was directly done in algal biodiesel waste residue containing solid agar plates supplemented with Nile red. Crude glycerol is a biodiesel waste whose bioconversion into value-added products provides an alternative for efficient management with dual benefit. For the scale-up studies of PHAs, Halomonas spp. especially H. daqingensis was observed as a potential candidate growing well in 3% Algal biodiesel waste residue (ABWR), 5% NaCl supplementation at 35°C within 48 h of incubation. Maximum Cell dry weight (CDW) of 0.362 ± 0.001 g and 0.236 ± 0.003 g PHA was obtained with H. daqingensis when grown in the fermentor with 0.5 vvm air flow rate and 200 rpm containing 3% ABWR supplemented with 5% NaCl at 35°C incubation temperature for 48 h. ABWR can serve as a sole substrate for PHA production at an industrial scale serving two approaches: getting rid of the biodiesel industrial waste containing high amount of glycerol besides using waste replacing commercial substrate thereby reducing the cost of the product.

Co‐utilization of amino acid‐rich wastes and glycerol for microbial lipid production

AbstractMicrobial lipids are considered to be potential raw materials for biodiesel production. However, the costs of such a process remain high due to the use of expensive feedstocks for microbial lipid production. The meat industry and biodiesel refineries generate amino acid (AA) wastes and crude glycerol, respectively, which could be explored as relatively cheap feedstocks for oleaginous yeasts. Unfortunately, AA wastes have a high nitrogen content and crude glycerol contains several impurities, discouraging microbial lipid production. Here, glycerol was co‐used with AA, or with AA blends with compositional profiles matching those of different meats, so that the media had favorable carbon‐to‐nitrogen (C/N) ratios to promote AA conversion into lipids using the oleaginous yeast Cryptococcus curvatus ATCC 20509 under two‐stage culture conditions. Co‐utilization of glycerol and AA resulted in improved lipid production. The highest lipid yield of 20.9 g 100 g–1 was achieved with lysine and glycerol, where the lipid yield was 13.9 g 100 g–1, using an AA blend of similar composition to sheep viscera and glycerol. The lipid products comprised over 93% of 16 and 18 carbon‐containing fatty acids, showing high potential for biodiesel production. The co‐use of glycerol with AA improved AA conversion into lipids while decreasing the inhibitory effects at relatively high AA concentrations. The utilization of crude glycerol and AA‐rich wastes from the meat industry could help both the development of biorefineries and waste minimization. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Effect of biohydrogen by overexpressing small RNA RyhB combined with ldh impairment in novel Klebsiella sp. FSoil 024

Biotechnological hydrogen production is considered as an environmentally sustainable alternative to petrochemical sources or electrolysis. Here, disruption of lactate dehydrogenase (LDH) and metabolic regulation via the small RNA RyhB were adopted to improve hydrogen production in the novel Klebsiella sp. strain FSoil 024. The hydrogen production of FSoil 024-L (Δldh) and FSoil 024-L/R (Δldh/RyhB) from glucose in a 5-L fermenter respectively increased by 40 and 50% compared to the wild type. When glycerol was adopted as a more favorable substrate, FSoil 024-L generated 3.3 L/L of hydrogen after 52 h of fermentation, implying its great potential for the utilization of crude glycerol to produce hydrogen. Overexpression of RyhB downregulated formate biosynthesis in FSoil 024, thereby redirecting NADH toward the hydrogen production pathway. This finding provides new insights into the role of cellular reducing power in hydrogen metabolism and establishes a rationale for improving hydrogen production.

Activation of Nano Kaolin Clay for Bio-Glycerol Conversion to a Valuable Fuel Additive

High production of biodiesel results in a surplus of glycerol as a byproduct that leads to a drastic decline in the glycerol price as well as overall biodiesel production. Alternative methods must be introduced for the economical process for biodiesel production via utilization of crude glycerol into valuable chemicals or fuel additives. This study introduces an ecofriendly process of solketal synthesis from glycerol and acetone in the presence of a novel metakaolin clay catalyst, which is a useful additive in biodiesel or gasoline, in order to enhance the octane number and to control the emissions. Moreover, kaolin clay catalysts are low cost, abundantly available, eco-friendly and one of the more promising applications for solketal synthesis. In this study, raw kaolin clay was activated with an easy acid activation technique, modification in physicochemical and textural properties were determined by using X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) and Field Emission Scanning Electron Microscope. Among all acid-treated catalysts, metakaolin K3 have shown best catalytic properties, high surface area and pore size after acid activation with 3.0 mol/dm3 at 98 °C for 3 h. Acetalization of glycerol with acetone carried out in the presence of an environmentally friendly and inexpensive novel metakaolin K3 catalyst. The maximum yield of solketal obtained was 84% at a temperature of 50 °C, acetone/glycerol molar ratio 6/1 and for 90 min with novel metakaolin clay catalyst. Effect of various parameters (time, temperature, acetone/glycerol molar ratio, catalyst loading) on the solketal yield and glycerol conversion was discussed in detail. This approach offers an effective way to transform glycerol into solketal—a desirable green chemical with future industrial applications.

Rewiring of glycerol metabolism in Escherichia coli for effective production of recombinant proteins

BackgroundThe economic viability of a protein-production process relies highly on the production titer and the price of raw materials. Crude glycerol coming from the production of biodiesel is a renewable and cost-effective resource. However, glycerol is inefficiently utilized by Escherichia coli.ResultsThis issue was addressed by rewiring glycerol metabolism for redistribution of the metabolic flux. Key steps in central metabolism involving the glycerol dissimilation pathway, the pentose phosphate pathway, and the tricarboxylic acid cycle were pinpointed and manipulated to provide precursor metabolites and energy. As a result, the engineered E. coli strain displayed a 9- and 30-fold increase in utilization of crude glycerol and production of the target protein, respectively.ConclusionsThe result indicates that the present method of metabolic engineering is useful and straightforward for efficient adjustment of the flux distribution in glycerol metabolism. The practical application of this methodology in biorefinery and the related field would be acknowledged.