Biotechnology for Biofuels最新文献

Sophorolipids (SLs) are glycolipid biosurfactants produced by non-pathogenic yeasts and represent a sustainable, biocompatible alternative to synthetic surfactants. Their amphiphilic architecture—comprising a hydrophilic sophorose headgroup and a hydrophobic fatty acid tail—confers excellent surface activity, emulsifying capacity, and a broad spectrum of biological effects. This review synthesizes advances since 2020 in understanding SL bioactivities, including antibacterial, antifungal, antibiofilm, antiviral, anti-inflammatory, antioxidant, and anticancer effects. We examine structure–activity relationships that govern functionality and survey strategies to enhance efficacy, such as chemical modification to generate novel derivatives and incorporation into nanostructures for targeted delivery. The review also evaluates application potential across sectors—agriculture (biopesticides, soil amendments), food (emulsifiers, preservatives), healthcare (therapeutics, coatings), and environmental remediation (oil and heavy-metal removal). Despite promising developments, challenges remain in production scaling, mechanistic clarity, and comprehensive characterization of novel SL. Addressing these issues will facilitate the integration of SLs into sustainable, high-value bioproducts aligned with green chemistry principles.

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Background

Hydrocarbon-based biofuels, known as drop-in fuels, which are chemically similar to petroleum, have gained significant attention. Microorganisms that produce medium-chain alkanes hold promise for the bioproduction of drop-in fuels. Previous studies identified Klebsiella sp. NBRC100048 as having aldehyde-decarbonylating activity, enabling it to convert aldehydes into alkanes. Using a genomic fosmid library from Klebsiella sp. NBRC100048, we identified open reading frame 2991 (orf2991), which catalyzes the conversion of tetradecanal to tridecane. This gene shares high sequence similarity with the aldehyde dehydrogenase (ALDH) family in Escherichia coli.

Results

ALDH homolog genes from Klebsiella sp. NBRC100048 and E. coli W3110 were cloned and expressed in E. coli to assess their potential alkane-synthesizing activity. Approximately one-fifth of the tested enzymes exhibited this function, with basic local alignment search tool (BLAST) analysis classifying them under the phenylacetaldehyde dehydrogenase, succinate-semialdehyde dehydrogenase, or aldehyde dehydrogenase B families. Testing additional ALDH homologs from diverse organisms—bacteria, fungi, plants, and animals—revealed that ALDHs with alkane-synthesizing activity are widespread, occurring in Gram-positive bacteria, actinomycetes, lactic acid bacteria, and yeast species. Alkane-synthesizing activity was observed with resting cells and cell-free extracts of the E. coli transformants expressing ALDH (ORF2991) from Klebsiella sp. NBRC100048 with aldehyde as the substrate in the presence of NADH. However, under the tested conditions, the purified enzyme alone did not show detectable decarbonylase activity. These results suggest that additional cellular components, cofactors, or specific conditions may be required for the purified enzyme to exhibit the activity.

Conclusions

We cloned several aldehyde dehydrogenases (ALDHs) from bacteria and yeast that have aldehyde decarbonylase activity to convert aldehydes to alkanes. Alkane-synthesizing activity was observed through the assays using resting cells and cell-free extracts of the E. coli transformants expressing ALDH. This novel function of aldehyde dehydrogenase introduces a new pathway for hydrocarbon fuel production and offers novel insights into microbial processes that may explain the natural origins of petroleum.

Ceiba pentandra (Kapok) has gained significant attention as a promising non-edible feedstock for biodiesel production, offering a sustainable alternative to traditional fossil fuels. The review provides a comprehensive analysis of the potential of Ceiba pentandra as an efficient biodiesel producer, including various aspects of cultivation, oil extraction, conversion processes, and future development. A scientometric analysis highlights the growing research interest in this area, while the geographical distribution and requirements of the plant site are discussed to illustrate its global availability. The review also discusses Ceiba pentandra’s adaptability and growth potential in diverse environments, its oil extraction methodologies, and its suitability for biodiesel production. It evaluates various techniques, examines their efficiency, and analyzes the effects on engine performance. The economic feasibility analysis assesses commercial potential and its role in sustainable development. Furthermore, the role of Ceiba pentandra in supporting Sustainable Development Goals (SDGs), such as clean energy and climate action, is explored. Current industry developments and future prospects, including advances in conversion technologies and supply chain optimization, are discussed. The review highlights the need for continued research and investment to realize Ceiba pentandra’s potential as a sustainable biodiesel source.

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Navigating the unpredictable nature of feedstock is crucial in bioprocessing. Manufacturing designs for homogeneous inputs to produce high-quality outputs, but biomass is inherently inconsistent. In bioethanol production, ethanol yield can depend on the type of corn itself in addition to the processing conditions to which it is subjected. While bioethanol processing adheres to standard operating conditions, there remains variability between facilities, an important point when considering the bioethanol byproduct DDGS as a commercial source for lutein and zeaxanthin extraction. Lutein and zeaxanthin are derived commercially from marigold flowers, which is chemically intensive and prohibits new players from entering the market. Exploring the potential of DDGS as a source of lutein and zeaxanthin would incentivize both corn growers and biorefineries but requires characterizing the differences in the yield potential of DDGS from separate bioethanol facilities. In this study, defatted DDGS from five Midwestern bioethanol facilities were examined using Soxhlet extraction with ethanol and subsequent HPLC analysis for lutein and zeaxanthin content. Using nonparametric methods and α = 0.05, it was determined that although facility appeared to have a significant effect on zeaxanthin yield, lutein yield displayed a greater degree of variability and differences in zeaxanthin yield could not be statistically ascribed to facility. Ultimately, the variability in corn growth and harvest and the downstream processing are too great to fully attribute any differences to facility alone. Future studies should consider sampling intermediate products throughout the biorefining process, as well as analyzing the incoming corn directly and comparing it to the final defatted DDGS to more fully understand how lutein and zeaxanthin partition and/or degrade during processing for a single variety of corn.

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Background

The recalcitrance of lignin is a major bottleneck in the efficient conversion of lignocellulosic biomass to bioethanol. Genetic reduction of lignin content represents a key strategy to overcome this barrier. This study focuses on characterizing the brown midrib2 (bm2) maize mutant to assess its potential for improving bioethanol production.

Results

Using a near-isogenic line (BC₄F₅) harboring the bm2 mutation, an 8.01% reduction in acid-insoluble lignin content in stalks was observed, with no significant change in cellulose or hemicellulose. This lignin reduction led to a 25.17% increase in glucose release upon sulfuric acid pretreatment. Most importantly, the bm2 mutant showed significantly higher lignocellulosic bioethanol yields: 3.05 g/L Ethanol 1 from the pretreatment hydrolysate (fermentation via Pichia stipites) and 25.88 g/L Ethanol 2 from the cellulose residue (fermentation via Saccharomyces cerevisiae), corresponding to 59.07% and 38.58% increases over the wild-type control, respectively.

Conclusions

Our results provide direct evidence that the bm2 mutation enhances lignocellulosic ethanol production by reducing lignin content and improving saccharification efficiency. This work underscores the value of bm2 in breeding specialized corn varieties for sustainable biofuel feedstock.

The β-glucan produced by Euglena gracilis has emerged as an alternative to traditional high-value biomolecule sources such as yeast and fungi to meet the rising demand. A UV-induced mutant strain, E. gracilis UV199, was developed using a novel aniline-blue-based screening method to increase production. The response surface methodology was used to optimize the growth medium, resulting in glucose and monosodium glutamate concentrations of 25.9 and 5.8 g/L, respectively, and 0.9 × Hutner medium. Using this medium resulted in a β-glucan productivity of 3.62 g/L/day, which was 114% higher than that achieved using the wild type E. gracilis. Productivity was further increased to 4.29 g/L/day through optimizing pH and temperature to 4.5 and 32 °C, respectively. A comprehensive framework was constructed for increasing microalgal β-glucan production through integrating strain and process development. Combining UV mutagenesis, rapid screening, and optimizing heterotrophic culture conditions is an effective strategy for producing functional biomaterials from E. gracilis, supporting its future commercialization in food, pharmaceutical, and cosmetic industries.

Genetic and metabolic engineering of Synechocystis sp. PCC 6803 has given rise to strains that produce a variety of bio-chemicals. Despite these successes, improvements in productivity metrics are required to achieve economically viable bio-production of carbon dioxide-derived compounds. Previously, environmental factors have been leveraged to increase product yields. Here, we optimise multiple environmental factors simultaneously using Design of Experiments (DOE) principles and find conditions that maximise L-lactate production. Light intensity, glycerol concentration, and light–dark cycle were found to be significant factors. Optimising these conditions resulted in a 6.3- and 7.4-fold increase in titre and yield. The results detailed here could have implications for metabolic engineering of, and bioprocesses using, Synechocystis sp. PCC 6803. In the future, DOE-mediated optimisation of environmental conditions could effectively maximise product titres from different production strains, or the enhanced conditions described here could be directly implemented in other metabolic engineering projects.

In order to achieve the resource utilization of black liquor and white mud. The new method which the self-steam gasification of black liquor and catalyzed with calcium oxide process is proposed for effectively treating the black liquor and obtaining the syngas and alkali. As results, 1.0 kg of SS can generate 0.714 kg-0.892 kg of syngas with its lower heating value ranging from 15.62 MJ/Nm³ to 10.10 MJ/Nm³. The solid products produce the regenerated alkaline solution with the causticizing efficiencies in the range of 50.48% to 80.45% after dissolved in water. Meanwhile, this new method can simplify the traditional pulping process. Therefore, it not only enables the resource utilization of the by-products from the pulping production process, but also reduces the energy consumption of alkali recovery and CO₂ emissions.

2-Hydroxy-3-methylvalerate (HMV), a kind of bioactive aliphatic 2-hydroxy acids, is a building block and a key intermediate for pharmaceuticals, including beauvericin, yet its microbial synthesis remains largely unexplored. Here, we present a synthetic biology strategy for high-titer production of HMV that couples mixed-sugar utilization with a division-of-labor microbial consortium. Co-feeding glucose and xylose synchronized substrate uptake with product formation, eliminating intermediate overflow and rerouting carbon from by-products into efficient HMV biosynthesis. To reduce the metabolic burden of the host, the HMV pathway is divided into two engineered strains: one optimized for glucose-to-intermediate conversion, the other for xylose-to-HMV completion. The best consortium, KMV-G-X, produces 2184.6 ± 111.8 mg/L HMV, comprising 82.2% of the total 2-hydroxy acids produced. Compared to mono-culture using glucose as a single substrate, this consortium exhibits less catabolic interference and enhanced HMV biosynthesis efficiency. This study shows that substrate utilization and pathway division of labor in synthetic consortium convert mixed sugars into high-value chemicals, boosting titer and robustness for scalable green production.

Background

The growing demand for sustainable lipid sources has fostered interest in single-cell oils from oleaginous yeasts as renewable alternatives to plant-derived and fossil-based oils, with applications in food, fuel, and material production. The oleaginous yeast Cutaneotrichosporon oleaginosus is of industrial relevance due to its ability to accumulate in excess of 60% (w/w) of its dry cell weight as lipids, while metabolizing a broad range of substrates. However, economic feasibility depends on improving productivity and adapting fatty acid profiles to application requirements.

Results

This study investigated the influence of temperature, pH, and dissolved oxygen concentration (DO) on lipid production and fatty acid composition in C. oleaginosus ATCC 20509. A three-level, three-factor Box–Behnken design was applied to assess their effects on lipid titer, oleate lipid titer, and the proportions of saturated and unsaturated fatty acids. Response surface methodology was used to develop quadratic models, identify optimized conditions, and predict fatty acid compositions. Temperature and pH significantly affected both overall lipid titer and degree of saturation. In fed-batch cultivation with consumption-based acetic acid feeding and glucose as the initial carbon source, lipid productivity increased to 0.38 g/L/h under the optimized oleate lipid titer condition (27.6 °C, pH 5.6, 10% DO) and to 0.39 g/L/h under the optimized saturated fatty acid condition (30 °C, pH 7.0, 10% DO), corresponding to 46% and 50% increases compared to literature values (0.26 g/L/h; 28 °C, pH 6.5, 50% DO). The fatty acid profile could thus be precisely modulated by adjusting the process parameters, achieving a difference in the saturation degree of more than 10%. Temperature was identified as the main factor influencing saturation, while pH enabled adjustment of the C16/C18 ratio, resulting in a modulation of palmitic acid fraction within the total triglycerides of up to 13%.

Conclusion

These findings highlight the potential of optimizing cultivation parameters based on reaction surface methodology to simultaneously improve lipid productivity and functionality by tailoring the fatty acid profile to the desired application requirements, without resorting to genetic engineering. Moreover, these insights support a circular bio-based economy by enabling an efficient production of tailored microbial oils as renewable alternatives to plant-derived lipids.

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