BioEnergy Research最新文献

Lignocellulosic biomass has diverse applications in bioenergy, biochemical, and biomaterial production. Enhancing these processes through pretreatment to obtain cellulose-rich material (CRM) using low transition temperature mixtures (LTTMs) is crucial. This study explores the impact of biomass type, LTTMs type, and heating methods on biomass pretreatment. Choline derivatives combined with glycerol were used for pretreatment of corncob, giant Juncao grass, and inflorescence hemp. Microwave irradiation heating was compared to conventional heating at 90 °C and 150 °C, with residence times of 5 and 10 min. The study demonstrated efficient breakdown of lignocellulosic structures to obtain CRMs. Corncob showed high-efficiency pretreatment with a 153% increase in cellulose content and 27% lignin removal. Pretreatment with LTTMs effectively increased cellulose content and delignification. The impact of different choline derivatives (ChCl, ChOAc, ChOH) was evident, with extraction efficiency influenced by anion type in the order OH⁻ > OAc⁻ > Cl⁻. The ChOH pretreatment increased cellulose content by 157% and lignin removal by 56%. Microwave-assisted heating surpassed conventional heating in lignocellulosic fractionation, achieving higher cellulose content and effective lignin removal. Microwave heating increased cellulose content by 343% and lignin removal by 82% at 150 °C, which was three times more than conventional heating, with a reaction time of 10 min compared to 720 min. Temperature and residence time were critical in lignin removal. The process allowed for the preservation of hemicellulose at lower temperatures or its extraction at higher temperatures.

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During the anaerobic digestion (AD) of food waste, the deliberate secession of substrate rapidly increases the microbial cell population, which can reach a maximum in 2–3 d. During short-term resting (STR), an increase in free NH₃ due to an increase in pH is a key inhibitor of cell proliferation; therefore, cell growth would be further promoted if free NH₃ was reduced. To explore adopting an STR technique to increase microbial cells in the AD of organic waste, we attempted to reduce free NH₃ by controlling the pH in the reactors. Two semi-continuously treated reactors were fed with food waste at a loading rate of 3.0 g-VS/L/d for 40 days and then the feeding was stopped in both reactors until day 47. One of the reactors was maintained at pH 7.37 ± 0.03, whereas pH was not controlled in the other. During STR, the cell density in the pH-controlled condition reached a maximum of 7.48 × 10¹⁰ cells/mL, which was twice as high as that before STR, and 1.7-times higher than that in the non-pH-controlled condition. These results demonstrated that mitigating NH₃ using pH can affect cell proliferation during STR.

The current study employs a tri-culture system, involving Trichoderma reesei and Penicillium janthinellum for cellulase production followed by the utilization of Saccharomyces cerevisiae for bioethanol production using pretreated rice straw as substrate. The fungal co-culture resulted in the production of maximum cellulase enzyme with the following activities: FPase, 1.09 IU/mL; CMCase, 24.47 IU/mL; beta-glucosidase, 4.74 IU/mL; and xylanase, 36.74 IU/mL respectively. Furthermore, the current work also represents a lesser studied aspect, concomitant biodetoxification, and cellulase production. Both T. reesei and P. janthinellum were able to metabolize the acid pretreatment by-products such as formic acid, acetic acid, HMF, and furfural. By implementing a cyclic shifting of temperature strategy, a maximum bioethanol titer of 17.05 g/L with a productivity of 0.405 g/(L × h) was achieved using the tri-culture system. This represents a 3.7-fold improvement compared to the SSF process conducted at the mutual optimum incubation temperature of 37 °C. This study presents a scope for a one-step process for fungal cellulase production and biodetoxification of the lignocellulose pretreated hydrolysate to avail an inhibitor-free medium for subsequent yeast co-culture for bioethanol production.

In this work, biochar was synthesized by carbonizing spent coffee grounds by conducting oxygen-limited pyrolysis in a muffle furnace. Six varieties of biochar have been synthesized at 550 ℃ and 750 ℃ with a ramp rate of 10 ℃/min and carbonization time of 120 min. Acid- and alkali-activated biochars were produced by carbonizing the activated biomass at 550 ℃ and 750 ℃. ZnCl₂ and KOH were used as activating agents for acid and alkali activation, respectively. All the synthesized biochar yield was recorded as 40–60 wt% of the biomass weight. BET surface area increased significantly after activation and the values varied between 1.01 and 720.52 m²/g. The process of chemical activation has resulted in increased BET surface area in comparison with the pristine biochar. Other characterizations include FESEM analysis, elemental analysis through EDX, FTIR, UV–visible spectroscopy, XRD analysis, TGA, and Raman spectroscopy. Raman spectra and UV–visible spectra of activated samples revealed a higher graphitic quality and absorbance, respectively, whereas XRD analysis demonstrated the changes in structural phases. Activated carbon based on spent coffee grounds has displayed higher thermal stability and better surface chemistry than pristine biochar, enabling its application in various domains that foster circular economy.

As carbon dioxide (CO₂) emissions rapidly increase, alternative strategies are needed to capture and mitigate carbon dioxide using microorganisms. To enhance CO₂ fixation and biomass production in microalgae, achieving the optimum concentration of dissolved carbon in the culture medium is essential. This study focuses on enhancing biomass production and CO₂ biofixation efficiency in Chlorella sp. BRE5 by increasing dissolved inorganic carbon (DIC) through the strategic use of sodium hydroxide (NaOH) and CO₂. Under shake flask study, the highest specific growth rate of 0.195 day⁻¹, biomass productivity of 123.2 mg/L/day, and CO₂ biofixation rate of 231.6 mg/L/day were found at NaOH dose of 0.25 g/L with CO₂ (1%, v/v) supplementation. Further, optimized NaOH with different supply strategies of 1% CO₂ was conducted in a photobioreactor (PBR) study. The best result was observed in PBR, where 1% CO₂ strategically sparged (3-day intervals) with optimum NaOH dose. Under this condition, biomass yield, CO₂ consumption rate, lipid productivity, and lipid content were found to be 2.25, 2.25, 4.19, and 1.87 times higher than the control. The outdoor cultivation of microalgae using a DIY bottle bioreactor (DIY BBR) was performed, resulting in less biomass and lipid productivity than that of the PBR study due to uncontrolled environmental conditions. The fatty acid methyl ester (FAME) profile comprised C16-C18 (84.86–90.69%), indicating the suitability for biodiesel production. This strategic supply of combined NaOH and CO₂ enhances DIC in the medium, facilitating both the CO₂ biofixation rate and biomass production.

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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.