BioEnergy Research最新文献

Rising concerns over fossil fuel depletion and plastic pollution have driven research into biodegradable alternatives, such as polylactic acid (PLA). Microbial fermentation is preferred for lactic acid production due to its ability to yield enantiomerically pure lactic acid, which is essential for PLA synthesis, unlike the racemic mixture from chemical synthesis. However, commercial lactic acid production using first-generation feedstocks faces challenges related to cost and sustainability. Macroalgae offer a promising alternative with their rapid growth rates and carbon capture capabilities. This review explores recent technological advancements in macroalgae physicochemical characterization, optimization of fermentation conditions, and innovative pretreatment methods to enhance sugar conversion rates for L-LA production. It also covers downstream processes for L-LA recovery, presenting a complete macroalgal biorefinery system. Environmental impacts and economic prospects are assessed through exergy and techno-economic analyses. By valorizing macroalgae detritus, this study underscores its potential to support a sustainable biorefinery industry, addressing economic feasibility and environmental impact.

Developing microbial consortia emerges as a new research frontier since complementing metabolisms provides new biotechnological capabilities for symbiotic interaction. To date, microalgal consortia with other microorganisms, such as fungi, bacteria, or other microalga are considered a biotechnological strategy to enhance microalgal physiological performance during CO₂ removal from biogas—a gaseous by-product composed mainly of methane (CH₄, 65–70%) and CO₂ (25–30%) considered an energy source due to its high methane content. Today, microalga-microorganism interaction studies have focused on developing diverse microbial consortia to increase CO₂ fixation of biogas and their metabolic changes during processing time. Thus, the present review proposes in a novel way the use of microalgal growth-promoting bacteria (MGPB) as a suitable partner to boost microalgal physiological performance and positively influence CO₂ fixation from biogas. Furthermore, the MGPB mechanisms involved during MGPB-microalga interaction to mitigate or regulate microalgae metabolism under the stressful condition of this gaseous effluent and improve their biotechnological uses focusing on CO₂ removal from biogas are analyzed and proposed. Additionally, the microalgal ability to convert CO₂ from biogas into high-value biotechnological compounds of commercial interest is analyzed, including the economic feasibility and scalability of a microalga-MGPB consortium. This physiological knowledge of microalga-MGPG consortia notably warrants its real impact on different economic sectors as a bio-economy overview. Furthermore, the discussion between engineering and biological sciences facilitates the development of suitable bioprocesses based on microalgae.

Salt stress on green microalgae increases lipid production at the cost of cellular homeostasis. Rapid optimization of growth conditions for high lipid productivity and biomass yield is crucial for translation to industrial-scale biodiesel production. To achieve this, the present study has developed a spectroscopic non-invasive analysis of lipid molecules produced by Chlamydomonas reinhardtii in two-stage salt stress, wherein 100 mM NaCl was added at two different time points: day 2 (D2 100) and day 4 (D4 100) of growth. Two-stage stress resulted in cell morphology like the photoautotrophic control grown in normal conditions, with negligible palmelloid formation in contrast to single-stage. Raman spectra acquired from ~ 30 individual cells in each culture revealed heterogeneities in lipid composition. Discrete wavelet transform decomposition of the Raman signal was used to enhance the signal-to-noise ratio and accuracy of Raman peak center estimation. An overall increase in heterogeneity indices for fatty acid degree of unsaturation was observed under two-stage salt stress: fourfold for D2 100 and ninefold for D4 100, especially at the stationary growth phase. The ratio of the CH₂/CH₃ scissoring mode (1440 cm⁻¹) and the C = O stretching mode (1750 cm⁻¹) reveals the shortening of fatty acid chain length in D4 100. Although Raman bands of lipids formed in all growth conditions are on average like Triolein (18:1), analyses of the degree of unsaturation (1656/1440 cm⁻¹) clarify the increased content of bi and tri-unsaturation only in D4 100. This non-invasive lipid profiling reveals that D4 100 is likely a non-ideal condition to obtain high-quality biodiesel-producing lipids. A comparative analysis of single-cell fluorescence microscopy of lipid droplets and Raman intensity of lipids shows the sensitivity of Raman intensity in deciphering the relative response of the cells to salt stress.

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The energy sector, currently dominated by fossil fuels, significantly contributes to carbon emissions and climate impacts. This study addresses the urgent need for renewable energy resources and promotes the utilization of waste from Malaysia’s palm oil industry. It proposes upgrading conventional palm oil mills to integrated mills to produce valuable biofuels such as methanol (MET) or dimethyl ether (DME). Using Aspen Plus V11 for simulation, mass and energy balances were provided for feasibility analysis, including techno-economic, exergy, and carbon analysis. The integrated process demonstrated 10 to 15% higher exergetic efficiency than conventional mills, enhancing the renewability index by 40% and reducing carbon emissions to 0.50 tonne CO₂ per tonne of palm oil. The integrated mills, operating at 61–64% exergetic efficiency, achieve a 28% reduction in exergy destruction when palm wastes are recovered and transformed into biofuels. Despite an 87% increase in non-renewable exergy consumption due to additional operating requirements, the overall renewability index remains high (around 0.9), demonstrating the commercial viability and environmental benefits of this approach. Overall, this study lays the foundation for integrated palm oil mill operation by utilizing palm waste to achieve net zero waste emissions, which is a positive outlook.

Biomass and organic residues are increasingly recognized as valuable resources for bioenergy production. Lignocellulosic biomass offers sustainable alternatives to fossil fuels for generation of bioenergy (such as biogas, bioethanol, biodiesel, and biohydrogen). Pretreatment plays a crucial role in a biomass biorefinery. It increases biomass homogeneity and production yields, thereby overcoming transportation and storage problems. However, the absence of a clear plan for biomass pretreatment represents a challenge for biomass conversion procedures. The socio-economic effects of biomass utilization are not unequivocally constructive. High investment and capital costs, technological maturity of biofuels, large-scale biomass supply, and policy and regulatory issues are among the key challenges. Despite these challenges, with the right strategies and solutions, complete biomass valorization is achievable. Solutions such as quick capital cost estimation, upgrading existing plants, optimizing biomass feedstock blends, utilizing waste biomass resources, and improving machinery efficiencies can address these challenges. Policy and regulatory challenges can be tackled through clear and long-term targets, financial and fiscal incentives, mandates and obligations, and sustainability governance supported by regulations and certifications. However, the realization of these benefits would depend on various factors such as the specific context of the biomass utilization, the available resources, and the market conditions. Thus, this work critically reviews the status of bioenergy production, the socio-economic challenges of biomass pretreatment, and its diversity in the bioenergy set-up.

Saponins are surface-active glycosides successfully applied to produce sugars via enzymatic hydrolysis and fermentation. However, there are several reports that saponins compromise the integrity of yeast cells, which would limit ethanol titers. In this context, the present study evaluated the role of saponins from sisal (Agave sisalana) on the action of cellulases and yeast within the context of cellulosic ethanol. Microcrystalline cellulose, pretreated coconut fiber samples, and pretreated corncob samples were evaluated as cellulose sources. Sisal saponins increased cellulolytic activity in adsorption (from 20.9 to 46.4%) and enzymatic hydrolysis (33.5 to 63.0%, using alkaline-pretreated coconut fiber as substrate). However, the amount of released sugars remained unchanged in tests with pretreated biomasses. Glucose released in the hydrolysis of microcrystalline cellulose reduced from 22.03 to 19.09 g/L using 10% (w/w) saponins. One percent (w/w) saponins caused an abrupt decrease in the viability of Saccharomyces cerevisiae cells within a few minutes (from 98.07 to 29.57% in 240 min), and ethanol was not produced in the simultaneous saccharification and fermentation. For this reason, sisal saponins have not replicated the success of other types of saponins and are unsuitable for cellulosic ethanol production.

Haematococcus pluvialis microalgae have emerged as a prevalent source of antioxidants in cosmetics and nutritional products. Additionally, numerous researchers have posited the potential of this microalgae to produce fatty acid methyl esters (FAME). Nevertheless, the optimization of the production of FAME from H. pluvialis oil has not been investigated. In this study, the transesterification reaction of H. pluvialis bio-oil was optimized using the response surface methodology, resulting in optimal experimental conditions for an oil to methanol ratio of 1:4.17, at a temperature of 80 °C, with a reaction time of 47 min. The resulting FAME was found to not comply with the biodiesel standard in terms of the content of polyunsaturated fatty acids (6.02%), as well as kinematic viscosity (7.02 mm²/s). Further study is required to reduce these parameters in order to ensure biodiesel quality and compliance with the standard. Nevertheless, its high flash point value of 150 °C and its high thermal stability within the temperature range of 211–290 °C suggest the potential for utilization as a biolubricant.

Electrocatalytic upgradation of biomass for chemicals and energy production is an emerging approach to address the environmental issues related to chemicals and energy production. If coupled with renewable energy, this approach will further enhance the sustainability goals for the future energy and chemical sector. This work critically reviews the progress on oxidative and reductive electrocatalytic upgrading of biomass-derived chemicals such as glycerol, sorbitol, levulinic acid, 5-hydroxymethylfurfural, furfural, and bio-oil to value-added products, including 2.5-dimethyl tetrahydrofuran, 2.5-dihydroxy methyl tetrahydro furan, 2-hydroxymethyl-5-(methyl amino methyl) furan, and 2,5-furan dicarboxylic acid with simulations production of hydrogen (H₂) energy. The role of the mediator in electrocatalytic upgradation serves as a high-efficiency catalytic platform for oxidation and reduction reactions. Pd and Ru exhibit promising attributes such as durability and superior electrocatalytic hydrogenation performance. Additionally, this review discusses various methods for enhancing biofuel through a multitude of approaches, such as hydrocracking, hydrotreatment, supercritical fluid processing, steam reforming, catalytic cracking, esterification, emulsification, hydrodeoxygenation, and electrocatalytic hydrogenation. Techno-economic assessment of electrocatalytic conversion of biomass to chemicals and energy are explored to identify the key contributing factors toward the economic viability of electrocatalytic upgradation of biomass for chemical and energy. Finally, research gaps are identified for further work along with economic assessment of electrocatalytic upgradation of biomass technology with and without integration of renewable energy.

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Effective pretreatment is essential for successfully utilizing renewable resources such as lignocellulosic biomass in the production of bioethanol. In this study, ternary deep eutectic solvents (DESs), namely choline chloride/lactic acid/glycerol (ChCl/LA/Gly), choline chloride/oxalic acid/glycerol (ChCl/OA/Gly), choline chloride/lactic acid/ethylene glycol (ChCl/LA/EG), and choline chloride/oxalic acid/ethylene glycol (ChCl/OA/EG) were prepared and employed for the pretreatment of cellulose-rich Napier grass (NG). Post treatment, the NG hydrolysate was subjected to enzymatic saccharification followed by ethanol fermentation. The results showed effective delignification of NG after treatment with the prepared ternary DESs, with ChCl/LA/EG removing a maximum of 92.89% lignin. The efficiency of the prepared DESs is attributed to their low densities, pH, and viscosity. Enzymatic saccharification of ChCl/LA/EG-treated NG resulted in a 1.68 fold increase in reducing sugar yield compared to that of untreated NG. All pretreated NG produced more bioethanol via a separate hydrolysis and fermentation (SHF) process than untreated NG after Saccharomyces cerevisiae fermentation. A maximum of 0.37 g bioethanol/g of biomass was obtained from the one-pot process using ChCl/LA/Gly pretreatment. FTIR and XRD analyses of untreated and pretreated NG corroborated the efficacy of the ternary DESs on cellulose recovery and delignification. Also, enzymatic and microbial inhibition studies on the prepared DESs show their potential to be employed in a one-pot process for biorefinery. The results of the present investigation show the potential of utilizing eco-friendly DESs and renewable resources for the production of bioethanol, a viable option to fossil fuels.

The study aimed to assess the efficiency of higher xylanase and lower cellulase-producing bacteria as a whole-cell biocatalyst for surface modification of banana pseudostem fibers in an eco-friendly and cost-effective manner. The ability of bacterial biocatalysts to alter fibers’ surface during fiber-biocatalyst interaction in liquid media was determined by analyzing fibers' chemical composition (cellulose, hemicellulose, and lignin), surface color, thickness, surface morphology, and spectral attributes. Results indicated that the production of xylanase by Bacillus licheniformis (1.23 IU/mg of protein) and Bacillus pumilus (1.29 IU/mg of protein) was almost 15 times more than cellulase produced by them. The content of alpha-cellulose (46.7%), hemicelluloses (21.6%), and lignin (11.7%) was slightly decreased in B. licheniformis-treated BPFs. The surface color (whiteness index) was positively improved, indicating color changes (ΔE) of 6.37 and 8.28 for B. pumilus and B. licheniformis-treated fibers, respectively. The thickness of fibers pretreated with B. lichenifiormis (160.75 ± 22.43 mm) and B. pumilus (202.655 ± 24.83) was reduced by 31.90 and 14.14%, respectively. Scanning electron micrograph studies revealed the increased roughness and grooves on the biocatalysts-treated fiber surface. Spectral analysis confirmed the stretching and deformation of inter and intra-molecular bonds of components of banana fibers. Briefly, the study highlights the effectiveness of whole-cell bacterial biocatalysts as a greener and cheaper tool for the surface modification of banana pseudostem fibers.