Woody biomass as a potential feedstock for fermentative gaseous biofuel production

Reversing lignin inhibition on enzymatic hydrolysis through regulating supramolecular assembly

The non-productive binding of enzymes to lignin is a well-documented barrier to efficient enzymatic hydrolysis. While significant attention has been paid to the influence of lignin's chemical structure on enzyme-lignin interactions, the role of its supramolecular assembly in this process has largely been overlooked. In this study, we regulated the supramolecular assembly of ethanol organosolv lignin (EOL) through solvent exchange dialysis and investigated its impact on the enzymatic hydrolysis of cellulose. Our findings reveal that tuning the supramolecular assembly of lignin significantly influenced its physicochemical properties, particularly particle size and hydrophobicity. Larger lignin particles, formed through self-assembly during dialysis, exhibited reduced hydrophobicity. Notably, the size of the lignin aggregates exercised very distinct effects on the performance of enzymatic hydrolysis. Certain large lignin assembled particles even reversed its inhibitory effects on the enzymatic hydrolysis of Avicel. EOL-M1 with the smallest particle size decreased 72 h glucose yields from 70.5 % to 62.9 %, whereas EOL-M100 with the largest particle size increased 72 h glucose yields to 82.3 %. Langmuir adsorption isotherms analysis, and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that lignin with larger particle sizes and lower hydrophobicity reduced the enzyme-binding capacity. Furthermore, this phenomenon was consistently validated with three different lignin samples obtained from organosolv and kraft pulping processes. This study demonstrated the unusual functions of lignin particles in the enzymatic saccharification process. It also provides new insights into the mechanism underlying the influences of lignin on enzyme-lignin interactions and bioprocessing at large.

Engineering the Metabolic Landscape of Microorganisms for Lignocellulosic Conversion

Bacteria and yeast are being intensively used to produce biofuels and high-added-value products by using plant biomass derivatives as substrates. The number of microorganisms available for industrial processes is increasing thanks to biotechnological improvements to enhance their productivity and yield through microbial metabolic engineering and laboratory evolution. This is allowing the traditional industrial processes for biofuel production, which included multiple steps, to be improved through the consolidation of single-step processes, reducing the time of the global process, and increasing the yield and operational conditions in terms of the desired products. Engineered microorganisms are now capable of using feedstocks that they were unable to process before their modification, opening broader possibilities for establishing new markets in places where biomass is available. This review discusses metabolic engineering approaches that have been used to improve the microbial processing of biomass to convert the plant feedstock into fuels. Metabolically engineered microorganisms (MEMs) such as bacteria, yeasts, and microalgae are described, highlighting their performance and the biotechnological tools that were used to modify them. Finally, some examples of patents related to the MEMs are mentioned in order to contextualize their current industrial use.

Using Alternative Sources of Energy for Decarbonization: A Piece of Cake, but How to Cook This Cake?

Few analytical or research works claim that the negative impact of improper use of ASEs may be comparable with that of hydrocarbons and sometimes even greater. It has become a common view that "green" energy (ASE) is clean, safe and environmentally friendly (eco-friendly) in contrast with "black" energy (hydrocarbons). We analyzed 144 works on systemic and/or comparative research of the modern and prospective ASE: biofuels, hydrogen, hydropower, nuclear power, wind power, solar power, geothermal power, oceanic thermal power, tidal power, wind wave power and nuclear fusion power. We performed our analysis within the Spaceship Earth paradigm. We conclude that there is no perfect ASE that is always eco-friendly. All ASEs may be dangerous to the planet considered as a closed and isolated unit ("spaceship") if they are used in an inconsistent manner. This is not in the least a reason to deny them as prospective sources of energy. Using all ASEs in different proportions in various regions of the planet, where their harm to the planet and humanity can be minimized and, on the contrary, their efficiency maximized, would give humanity the opportunity to decarbonize the Earth, and make the energy transition in the most effective way.