INFORM October 2025

32 • inform October 2025, Vol. 36 (9)

Contiguous supplementation of bicarbonate and carbon dioxide to improve carbon utilization efficiency and biodiesel production from a single-cell alga Chlamydomonas reinhardtii Samantaray, S., et al. , Renewable Energy , 245,122779, 2025. https://doi.org/10.1016/j.renene.2025.122779 This work established a promising hybrid carbon absorp tion-biofixation of CO 2 approach, that benefit of having an adequate carbon supply allowed for the creation of an efficient buffer system that maintained a constant pH and enough dissolved inorganic carbon (DIC) for photosynthesis to improve biomass and lipid production in the single-cell green alga Chlamydomonas reinhardtii . In a 5L photobioreactor, the microalga C. reinhardtii exhibited better performance with 6 % CO 2 enriched air (0.4 vvm flow rate) and NaHCO 3 concentration of 5 mM on 3rd day of supplementation in nutrient sufficient medium. This included a maximum specific growth rate of 0.462 d −1 , a biomass yield of 3.79 g L −1 , a biomass productivity of 0.63 g L −1 d −1 , and a total lipid content of 43.7 % (dcw). This com petitive growth rates might only be possible, when the medium contained high amount of DIC up to 103 mg L −1 . The pH data demonstrated that bicarbonate consumption can effectively raise pH levels, which can be countered by CO 2 supplementation to keep the medium within the ideal range for algal growth throughout the whole cultivation period. It was found that the maximal rate of CO 2 bio-fixation reached up to 1.18 g L −1 d −1 . This study demon strates that 6 % CO 2 with 5 mM NaHCO 3 (supplemented on 3rd day of incubation) as the inorganic carbon sources followed by nitrogen deficiency induces synthesis of high levels of lipid up to 1.67 g L −1 (57 % dcw) in C. reinhardtii. The presence of suitable fatty acid profile including palmitic, palmitoleic, oleic, linoleic, lin olenic and stearic acid methyl esters demonstrated that the algal lipids could fulfil the requirements for standard fuel properties of biodiesel. Yarrowia lipolytica uses olive tree prunings hydrolysates for microbial lipids as biodiesel feedstock Dias, B., et al. , Chemical Engineering Science , 305, 121150, 2025. https://doi.org/10.1016/j.ces.2024.121150 Efficiently valorizing olive tree prunings (OTP) for microbial lipids represents an excellent strategy to achieve resource circular ity, accompanied by economic and environmental benefits. Since the production of lipids from OTP hydrolysate (OTPH) by yeasts remains underexplored, this study investigated the potential of Y. lipolytica to produce lipid-rich biomass in bioreactor batch cultures. OTP was fractionated by combining hydrothermal pretreatment with enzymatic hydrolysis, obtaining a glucose-rich (125 g/L) OTPH. Undiluted OTPH proved to be a suitable substrate, lead ing to the production of 78 g/L biomass, enriched with 26.8 g/L lipids, and 25 g/L citric acid. The lipids concentration achieved is

the highest reported for yeasts in lignocellulosic biomass hydroly sates. Intracellular lipids were highly unsaturated, mainly com posed of oleic acid. The estimated properties of biodiesel that would be obtained using Y. lipolytica lipids are per international standards. This study is a starting point for a potential biorefinery approach using OTP as a raw material for biodiesel production.

nnn

Ignacio Vieitez is a research professor at the Universdad de la República in Montevideo, Uruguay. He studies green extraction processes to isolate bioactive compounds and determines their potential benefits as food ingredients.

Biotechnology provides a wide array of advanced tools for optimiz ing the production, extraction, and application of natural antiox idants. These bioactive compounds, predominantly derived from plant sources, are essential for mitigating oxidative stress by neu tralizing free radicals, thereby contributing to the prevention of various chronic diseases such as cardiovascular disorders, neuro degenerative conditions, and certain types of cancer. Modern bio technological strategies, (including plant tissue culture, metabolic engineering, and nanotechnology), are being intensively explored to enhance not only the yield and consistency of antioxidant pro duction but also their stability and bioavailability. Plant tissue culture enables the controlled and sustainable production of anti oxidant-rich metabolites under sterile and reproducible condi tions. Metabolic engineering allows for the targeted modification of biosynthetic pathways to increase the accumulation of specific antioxidant compounds. Additionally, the incorporation of nano technology offers innovative delivery systems that can improve the solubility, controlled release, and absorption of these natural anti oxidants in the human body. Collectively, these approaches repre sent a promising frontier in maximizing the therapeutic potential and commercial viability of plant-derived antioxidants. Biotechnological production and emerging applications of betalains: A review Khan, M. I. and Polturak, G., Biotechnology Advances , 81, 108576, 2025. https://doi.org/10.1016/j.biotechadv.2025.108576 Betalains are food-grade hydrophilic pigments with antioxidant and biological activities, predominantly found in plants. Betanin is a red-violet betalain synthesized from tyro sine through L-DOPA formation, its subsequent aromatic ring opening, spontaneous cyclization to betalamic acid, and then pH-dependent condensation with i) cyclo‐DOPA-5- O -glucoside or ii) cyclo‐DOPA followed by 5- O -glucosylation. This short path way in plants for betanin biosynthesis has been heterologously expressed in other organisms (e.g. non-betalainic plants, yeasts,