Itaconic acid production from undetoxified enzymatic hydrolysate of bamboo residues using Aspergillus terreus

Harnessing agro-industrial waste: Enzyme-driven biosynthesis in Itaconic acid production

Itaconic acid (IA) is a highly soluble and stable bio-based chemical with diverse industrial applications, particularly in sustainable material production. Despite the growing demand for bio-based IA, efficient and sustainable production methods remain a challenge, particularly in optimizing fungal fermentation and by-product utilization. This study explores the synergistic use of solid-state fermentation utilizing Aspergillus awamori for enzyme production and hydrolysis, combined with submerged fermentation to optimize IA bioproduction from wheat bran by-products. The optimal levels of enzyme production observed on the third day were closely related to moisture's vital role in synthesis dynamics, influencing glucose concentration and enzyme activities. The activities of glucoamylase, cellulase, and endoglucanase exceeded 50 U/g, 55 FPU/g, and 15 U/g, respectively. Subsequent IA bioproduction using A. terreus was optimized under various initial pH levels, with pH 4 and 5 demonstrating superior IA yields of 8.082 ± 0.19 g/L and 10.782 ± 0.98 g/L, respectively. Scaling up challenges highlight the need for a 30 % enzyme extract in wheat bran hydrolysis, with economic favorability and achieving a 52 % IA conversion efficiency from citric acid. This approach underscores sustainable IA production from agro-industrial by-products, aiding the circular economy and bio-based processes.

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.

Mycoproteins and their health-promoting properties: Fusarium species and beyond

Filamentous fungal mycoproteins have gained increasing attention as sustainable alternatives to animal and plant-based proteins. This comprehensive review summarizes the nutritional characteristics, toxicological aspects, and health-promoting effects of mycoproteins, focusing on those derived from filamentous fungi, notably Fusarium venenatum. Mycoproteins are characterized by their high protein content, and they have a superior essential amino acid profile compared to soybeans indicating excellent protein quality and benefits for human nutrition. Additionally, mycoproteins offer enhanced digestibility, further highlighting their suitability as a protein source. Furthermore, mycoproteins are rich in dietary fibers, which have been associated with health benefits, including protection against metabolic diseases. Moreover, their fatty acids profile, with significant proportions of polyunsaturated fatty acids and absence of cholesterol, distinguishes them from animal-derived proteins. In conclusion, the future of mycoproteins as a health-promoting protein alternative and the development of functional foods relies on several key aspects. These include improving the acceptance of mycoproteins, conducting further research into their mechanisms of action, addressing consumer preferences and perceptions, and ensuring safety and regulatory compliance. To fully unlock the potential of mycoproteins and meet the evolving needs of a health-conscious society, continuous interdisciplinary research, collaboration among stakeholders, and proactive engagement with consumers will be vital.

Improved consolidated bioprocessing for itaconic acid production by simultaneous optimization of cellulase and metabolic pathway of Neurospora crassa

Lignocellulose was directly used in itaconic acid production by a model filamentous fungus Neurospora crassa. The promoters of two clock control genes and cellobiohydrolase 1 gene were selected for heterologous genes expression by evaluating different types of promoters. The effect of overexpression of different cellulase was compared, and it was found that expression of cellobiohydrolase 2 from Trichoderma reesei increased the filter paper activity by 2 times, the cellobiohydrolase activity by 4.5 times, and that the itaconic acid titer was also significantly improved. A bidirectional cis-aconitic acid accumulation strategy was established by constructing the reverse glyoxylate shunt and expressing the transporter MTTA, which increased itaconic acid production to 637.2 mg/L. The simultaneous optimization of cellulase and metabolic pathway was more conducive to the improvement of cellulase activity than that of cellulase alone, so as to further increase itaconic acid production. Finally, through the combination of fermentation by optimized strains and medium optimization, the titers of itaconic acid using Avicel and corn stover as substrate were 1165.1 mg/L and 871.3 mg/L, respectively. The results prove the potential of the consolidated bioprocessing that directly converts lignocellulose to itaconic acid by a model cellulase synthesizing strain.

Utilization of sweet sorghum juice as a carbon source for enhancement of itaconic acid production in engineered Corynebacterium glutamicum

Itaconic acid is a promising biochemical building block that can be used in polymer synthesis. Itaconic acid is currently produced in industry by the natural producer fungus Aspergillus terreus using glucose as a main carbon source. Most research for itaconic acid production using lignocellulosic-based carbon sources was carried out by A. terreus. Engineered Corynebacterium glutamicum strain which can grow in presence of fermentation inhibitors without effect on growth, was used for production of itaconic acid using sweet sorghum juice and bagasse sugar lysate (BSL). BSL contains many inhibitors unlike sorghum juice. C. glutamicum could grow in the media containing both types of lignocellulose-based carbon sources without showing any growth inhibition, however, sorghum juice was better in itaconic acid production than BSL. Different constructed strains of C. glutamicum were used for itaconic acid production, however, C. glutamicum ATCC 13032 pCH-Tad1optAdi1opt strain expressing Adi1/Tad1 genes (trans-pathway) from Ustilago maydis proved to be better in itaconic acid production giving final titer of 8.4 and 4.02 g/L using sweet sorghum juice and BSL as the sole carbon sources by fed-batch fermentation. Our study is the first for production of itaconic acid using sweet sorghum juice and BSL. The present study also proved that C. glutamicum can be used for enhancing itaconic acid production using lignocellulosic-based carbon sources.

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

Microbial biomanufacturing is a promising approach to produce high-value compounds with low-carbon footprint and significant economic benefits. Among twelve "Top Value-Added Chemicals from Biomass", itaconic acid (IA) stands out as a versatile platform chemical with numerous applications. IA is naturally produced by Aspergillus and Ustilago species through a cascade enzymatic reaction between aconitase (EC 4.2.1.3) and cis-aconitic acid decarboxylase (EC 4.1.1.6). Recently, non-native hosts such as Escherichia coli, Corynebacterium glutamicum, Saccharomyces cerevisiae, and Yarrowia lipolytica have been genetically engineered to produce IA through the introduction of key enzymes. This review provides an up-to-date summary of the progress made in IA bioproduction, from native to engineered hosts, covers in vivo and in vitro approaches, and highlights the prospects of combination tactics. Current challenges and recent endeavors are also addressed to envision comprehensive strategies for renewable IA production in the future towards sustainable development goals (SDGs).

Enhanced production of itaconic acid from enzymatic hydrolysate of lignocellulosic biomass by recombinant Corynebacteriumglutamicum

Itaconic acid (IA) is a value-added chemical currently produced by Aspergillus terreus from edible glucose and starch but not from inedible lignocellulosic biomass owing to the high sensitivity to fermentation inhibitors present in the hydrolysate of lignocellulosic biomass. To produce IA from lignocellulosic biomass, a gram-positive bacterium, Corynebacterium glutamicum, with a high tolerance to fermentation inhibitors was metabolically engineered to express a fusion protein composed of cis-aconitate decarboxylase from A. terreus responsible for IA formation from cis-aconitate and a maltose-binding protein (malE) from Escherichia coli. The codon-optimized cadA_malE gene was expressed in C. glutamicum ATCC 13032, and the resulting recombinant strain produced IA from glucose. IA concentration increased 4.7-fold by the deletion of the ldh gene encoding lactate dehydrogenase. With the Δldh strain HKC2029, an 18-fold higher IA production was observed from enzymatic hydrolysate of kraft pulp as a model lignocellulosic biomass than from glucose (6.15 and 0.34 g/L, respectively). The enzymatic hydrolysate of kraft pulp contained various potential fermentation inhibitors involved in furan aldehydes, benzaldehydes, benzoic acids, cinnamic acid derivatives, and aliphatic acid. Whereas cinnamic acid derivatives severely inhibited IA production, furan aldehydes, benzoic acids, and aliphatic acid improved IA production at low concentrations. The present study suggests that lignocellulosic hydrolysate contains various potential fermentation inhibitors; however, some of them can serve as enhancers for microbial fermentation likely due to the changing of redox balance in the cell.

Recent Advances on the Production of Itaconic Acid via the Fermentation and Metabolic Engineering

Itaconic acid (ITA) is one of the top 12 platform chemicals. The global ITA market is expanding due to the rising demand for bio-based unsaturated polyester resin and its non-toxic qualities. Although bioconversion using microbes is the main approach in the current industrial production of ITA, ecological production of bio-based ITA faces several issues due to: low production efficiency, the difficulty to employ inexpensive raw materials, and high manufacturing costs. As metabolic engineering advances, the engineering of microorganisms offers a novel strategy for the promotion of ITA bio-production. In this review, the most recent developments in the production of ITA through fermentation and metabolic engineering are compiled from a variety of perspectives, including the identification of the ITA synthesis pathway, the metabolic engineering of natural ITA producers, the design and construction of the ITA synthesis pathway in model chassis, and the creation, as well as application, of new metabolic engineering strategies in ITA production. The challenges encountered in the bio-production of ITA in microbial cell factories are discussed, and some suggestions for future study are also proposed, which it is hoped offers insightful views to promote the cost-efficient and sustainable industrial production of ITA.

A consolidated review of commercial-scale high-value products from lignocellulosic biomass

For decades, lignocellulosic biomass has been introduced to the public as the most important raw material for the environmentally and economically sustainable production of high-valued bioproducts by microorganisms. However, due to the strong recalcitrant structure, the lignocellulosic materials have major limitations to obtain fermentable sugars for transformation into value-added products, e.g., bioethanol, biobutanol, biohydrogen, etc. In this review, we analyzed the recent trends in bioenergy production from pretreated lignocellulose, with special attention to the new strategies for overcoming pretreatment barriers. In addition, persistent challenges in developing for low-cost advanced processing technologies are also pointed out, illustrating new approaches to addressing the global energy crisis and climate change caused by the use of fossil fuels. The insights given in this study will enable a better understanding of current processes and facilitate further development on lignocellulosic bioenergy production.

Environmental assessment of the production of itaconic acid from wheat straw under a biorefinery approach

This study performs the environmental assessment of itaconic acid (IA) production from wheat straw. The Life Cycle Assessment (LCA) methodology is used to determine the environmental hotspots, considering impact categories such as Global Warming (GW), Fossil Resource Scarcity (FRS), Water Consumption (WC), among others. A sensitivity analysis was performed considering an optimization of the steam explosion process and 100% renewable energy. Results report an impact of about 14.33 kg CO₂ eq in GW, 4.15 kg of oil eq in FRS, for each kg of IA produced for the baseline scenario. Moreover, the pretreatment and fermentation stages constitute hotspots of the IA production. In addition, using a renewable energy source in production would reduce the impact by 82% in GW, 71% in PM and 82% in FRS categories. The optimization of the steam explosion process presents a better performance in GW and FRS but also lies in an increase in WC.

Recent advances in lignocellulosic biomass white biotechnology for bioplastics

Lignocellulosic biomass has great potential as an inedible feedstock for bioplastic synthesis, although its use is still limited compared to current edible feedstocks of glucose and starch. This review focuses on recent advances in the production of biopolymers and biomonomers from lignocellulosic feedstocks with downstream processing and chemical polymer syntheses. In microbial production, four routes composed of existing poly (lactic acid) and polyhydroxyalkanoates (PHAs) and the emerging biomonomers of itaconic acid and aromatic compounds were presented to review present challenges and future perspectives, focusing on the use of lignocellulosic feedstocks. Recently, advances in purification technologies decreased the number of processes and their environmental burden. Additionally, the unique structures and high-performance of emerging lignocellulose-based bioplastics have expanded the possibilities for the use of bioplastics. The sequence of processes provides insight into the emerging technologies that are needed for the practical use of bioplastics made from lignocellulosic biomass.

Microbial itaconic acid production from starchy food waste by newly isolated thermotolerant Aspergillus terreus strain

In the present study, we have explored the potential of newly isolated Aspergillus terreus BD strain, which can accumulate itaconic acid (IA) at higher temperature. The shake flask cultivation of thermotolerant strain with medium optimized using Box-Behnken Design at 45 °C resulted in IA accumulation of 28.9 g/L with yield of 0.27 g/g. The enzymatic saccharification of the synthetic food waste (SFW) consisting of potatoes, rice & noodles were optimized using Taguchi method of orthogonal array to maximize the release of fermentable sugar. The maximum glucose release of 0.60 g/g was achieved with 10% biomass loading, 5% enzyme concentration, pH 5.5 and temperature 60 ⁰C. The sugars obtained from SFW was integrated with IA production and maximum IA titer achieved with SFW hydrolysate during bioreactor cultivation was 41.1 g/L with conversion yield of 0.27 g/g while with pure glucose IA titer and yield were 44.7 g/L and 0.30 g/g, respectively.

Recent advances in the valorization of plant biomass

Plant biomass is a highly abundant renewable resource that can be converted into several types of high-value-added products, including chemicals, biofuels and advanced materials. In the last few decades, an increasing number of biomass species and processing techniques have been developed to enhance the application of plant biomass followed by the industrial application of some of the products, during which varied technologies have been successfully developed. In this review, we summarize the different sources of plant biomass, the evolving technologies for treating it, and the various products derived from plant biomass. Moreover, the challenges inherent in the valorization of plant biomass used in high-value-added products are also discussed. Overall, with the increased use of plant biomass, the development of treatment technologies, and the solution of the challenges raised during plant biomass valorization, the value-added products derived from plant biomass will become greater in number and more valuable.

Consolidated bioprocessing of cellulose to itaconic acid by a co-culture of Trichoderma reesei and Ustilago maydis

BACKGROUND

Itaconic acid is a bio-derived platform chemical with uses ranging from polymer synthesis to biofuel production. The efficient conversion of cellulosic waste streams into itaconic acid could thus enable the sustainable production of a variety of substitutes for fossil oil based products. However, the realization of such a process is currently hindered by an expensive conversion of cellulose into fermentable sugars. Here, we present the stepwise development of a fully consolidated bioprocess (CBP), which is capable of directly converting recalcitrant cellulose into itaconic acid without the need for separate cellulose hydrolysis including the application of commercial cellulases. The process is based on a synthetic microbial consortium of the cellulase producer Trichoderma reesei and the itaconic acid producing yeast Ustilago maydis. A method for process monitoring was developed to estimate cellulose consumption, itaconic acid formation as well as the actual itaconic acid production yield online during co-cultivation.

RESULTS

The efficiency of the process was compared to a simultaneous saccharification and fermentation setup (SSF). Because of the additional substrate consumption of T. reesei in the CBP, the itaconic acid yield was significantly lower in the CBP than in the SSF. In order to increase yield and productivity of itaconic acid in the CBP, the population dynamics was manipulated by varying the inoculation delay between T. reesei and U. maydis. Surprisingly, neither inoculation delay nor inoculation density significantly affected the population development or the CBP performance. Instead, the substrate availability was the most important parameter. U. maydis was only able to grow and to produce itaconic acid when the cellulose concentration and thus, the sugar supply rate, was high. Finally, the metabolic processes during fed-batch CBP were analyzed in depth by online respiration measurements. Thereby, substrate availability was again identified as key factor also controlling itaconic acid yield. In summary, an itaconic acid titer of 34 g/L with a total productivity of up to 0.07 g/L/h and a yield of 0.16 g/g could be reached during fed-batch cultivation.

CONCLUSION

This study demonstrates the feasibility of consortium-based CBP for itaconic acid production and also lays the fundamentals for the development and improvement of similar microbial consortia for cellulose-based organic acid production.