Microbial itaconic acid bioproduction towards sustainable development: Insights, challenges, and prospects

Issatchenkia orientalis as a platform organism for cost-effective production of organic acids

Driven by the urgent need to reduce the reliance on fossil fuels and mitigate environmental impacts, microbial cell factories capable of producing value-added products from renewable resources have gained significant attention over the past few decades. Notably, non-model yeasts with unique physiological characteristics have emerged as promising candidates for industrial applications, particularly for the production of organic acids. Among them, Issatchenkia orientalis stands out for its exceptional natural tolerance to low pH and high osmotic pressure, traits that are critical for overcoming the limitations of conventional microbial organisms. The acid tolerance of I. orientalis enables organic acid production under low pH conditions, bypassing the need for expensive neutral pH control typically required in conventional processes. Organic acids produced by I. orientalis, such as lactic acid, succinic acid, and itaconic acid, are widely used as building blocks for bioplastics, food additives, and pharmaceuticals. This review summarizes the key findings from systems biology studies on I. orientalis over the past two decades, providing insights into its unique metabolic and physiological traits. Advances in genetic tool development for this non-model yeast are also discussed, enabling targeted metabolic engineering to enhance its production capabilities. Additionally, case studies are highlighted to illustrate the potential of I. orientalis as a platform organism. Finally, the remaining challenges and future directions are addressed to further develop I. orientalis into a robust and versatile microbial cell factory for sustainable biomanufacturing.

Itaconic acid production from corn stover hydrolysates for a newly isolated Aspergillus terreus through adaptive evolution

Itaconic acid can be produced using lignocellulosic biomass; however, the inhibitors from pretreatment process of biorefinery are toxic to the fermenting strains. Here, with 35.70 ± 0.69 g/L (0.19 ± 0.05 g/L·h and 73.84 ± 0.01%) itaconic acid from shake flask fermentation of synthetic medium (SM), a newly isolated Aspergillus terreus just produced 1.01 ± 0.01 g/L itaconic acid from corn stover hydrolysates (CSH) for the serious block of aldehyde inhibitors and acetic acid. Convincingly, 25.34 ± 3.94 g/L (0.13 ± 0.02 g/L·h and 37.92 ± 3.89%) itaconic acid was achieved from the detoxified CSH (with residual 0.49 g/L acetic acid) using 4.0% activated charcoal. 21.64 ± 2.42 g/L (0.05 ± 0.01 g/L·h and 26.96 ± 7.81%) itaconic acid was further achieved from CSH for the adapted A. terreus with better degradation ability of furanic aldehydes and phenolic aldehydes. Furthermore, the 108 mutation sites of nine genes from adaptive laboratory evolution (ALE) for A. terreus were further uncovered through single nucleotide polymorphisms (SNPs) analysis, and thus would be responsible for the improved fermentability of itaconic acid from CSH. The current work broke the bottlenecks in itaconic acid fermentation directly from CSH through improving A. terreus using directed evolution technique, and thus would provide a strain biocatalyst A. terreus and establish the alternative strategy to efficiently produce itaconic acid using corn stover.

Cellulose Acetates in Hydrothermal Carbonization: A Green Pathway to Valorize Residual Bioplastics

Bioplastics possess the potential to foster a sustainable circular plastic economy, but their end-of-life is still challenging. To sustainably overcome this problem, this work proposes the hydrothermal carbonization (HTC) of residual bioplastics as an alternative green path. The focus is on cellulose acetate - a bioplastic used for eyewear, cigarette filters and other applications - showing the proof of concept and the chemistry behind the conversion, including a reaction kinetics model. HTC of pure and commercial cellulose acetates was assessed under various operating conditions (180-250 °C and 0-6 h), with analyses on the solid and liquid products. Results show the peculiar behavior of these substrates under HTC. At 190-210 °C, the materials almost completely dissolve into the liquid phase, forming 5-hydroxymethylfurfural and organic acids. Above 220 °C, intermediates repolymerize into carbon-rich microspheres (secondary char), achieving solid yields up to 23 %, while itaconic and citric acid form. A comparison with pure substrates and additives demonstrates that the amounts of acetyl groups and derivatives of the plasticizers are crucial in catalyzing HTC reactions, creating a unique environment capable of leading to a total rearrangement of cellulose acetates. HTC can thus represent a cornerstone in establishing a biorefinery for residual cellulose acetate.

Enhanced production of isobutyl and isoamyl acetate using Yarrowia lipolytica

Short-chain esters, particularly isobutyl acetate and isoamyl acetate, hold significant industrial value due to their wide-ranging applications in flavors, fragrances, solvents, and biofuels. In this study, we demonstrated the biosynthesis of acetate esters using Yarrowia lipolytica as a host by feeding alcohols to the yeast culture. Initially, we screened for optimal alcohol acyltransferases for ester biosynthesis in Y. lipolytica. Strains of Y. lipolytica expressing atf1 from Saccharomyces cerevisiae, produced 251 or 613 mg/L of isobutyl acetate or of isoamyl acetate, respectively. We found that introducing additional copies of ATF1 enhanced ester production. Furthermore, by increasing the supply of acetyl-CoA and refining the culture conditions, we achieved high production of isoamyl acetate, reaching titers of 3404 mg/L. We expanded our study to include the synthesis of a range of acetate esters, facilitated by enriching the culture medium with various alcohols. This study underscores the versatility and potential of Y. lipolytica in the industrial production of acetate esters.

Development of ultra-thin poly(L-lactic acid)-based films integrating toughness, barrier properties, and gas selectivity: Towards gas-permeation controllable green food packaging

High costs and low performance have constrained the application of bio-based materials in food packaging. Herein, a series of ultra-thin poly(L-lactic acid-iconic acid N-diol) (P(LA-NI)) copolymer films were developed using a "one-step" polycondensation process with integrated toughness, barrier properties, gas selectivity, and quality control features. The massive branched structure and gg conformers in P(LA-NI) act as "internal chain expansion" and "internal plasticization". Meanwhile, P(LA-NI) contains numerous polar groups and unique nanoscale microphase structures to realize excellent CO2, O2 barrier, CO2/O2 selectivity, anti-fogging, and UV shielding functions. The atmosphere within the package spontaneously achieves the desirable low O2 and high CO2 levels when packaging button mushrooms with high respiratory metabolism. Eventually, the shelf life of button mushrooms reached 24 days, >3-fold extended. This PLLA-based film meets "dual carbon" and "food safety" goals and has vast potential for fresh food preservation.

Bio-Sourced, High-Performance Carbon Fiber Reinforced Itaconic Acid-Based Epoxy Composites with High Hygrothermal Stability and Durability

Thermosetting polymers and composites are a class of high-performance materials with significant industrial applications. However, the widespread use of thermosets and their composites generates large quantities of waste and leads to serious economic and environmental problems, there is a critical need in the elaboration of sustainable composite materials. Here, we propose a method to prepare sustainable carbon fiber reinforced composites with different degrees of greenness by blending environmentally friendly EIA with DGEBA in different ratios, and the properties compared with a well-known commercial petroleum-based epoxy resin. The prepared carbon fiber reinforced polymer (CFRP) composites with different degrees of greenness had excellent dimensional stability under extreme hygrothermal aging. After aging, the green CFRP composite T700/EIA-30 has higher strength and performance retention than that of petroleum-based CFRP composites. The higher hygrothermal stability and durability of EIA-based epoxy resins as compared with BPA-based epoxy resins demonstrated significant evidence to design and develop a novel bio-based epoxy resin with high performance to substitute the petroleum-based epoxy resin.

Secondary metabolites from the deep-sea derived fungus Aspergillus terreus MCCC M28183

Aspergillus fungi are renowned for producing a diverse range of natural products with promising biological activities. These include lovastatin, itaconic acid, terrin, and geodin, known for their cholesterol-regulating, anti-inflammatory, antitumor, and antibiotic properties. In our current study, we isolated three dimeric nitrophenyl trans-epoxyamides (1-3), along with fifteen known compounds (4-18), from the culture of Aspergillus terreus MCCC M28183, a deep-sea-derived fungus. The structures of compounds 1-3 were elucidated using a combination of NMR, MS, NMR calculation, and ECD calculation. Compound 1 exhibited moderate inhibitory activity against human gastric cancer cells MKN28, while compound 7 showed similar activity against MGC803 cells, with both showing IC50 values below 10 μM. Furthermore, compound 16 exhibited moderate potency against Vibrio parahaemolyticus ATCC 17802, with a minimum inhibitory concentration (MIC) value of 7.8 μg/mL. This promising research suggests potential avenues for developing new pharmaceuticals, particularly in targeting specific cancer cell lines and combating bacterial infections, leveraging the unique properties of these Aspergillus-derived compounds.