Komagataella phaffii (aka Pichia pastoris) is a yeast able to grow in methanol as the sole carbon and energy source. This substrate is converted into formaldehyde, a toxic intermediary that can either be assimilated to biomass or dissimilated to CO₂ through the enzymes formaldehyde dehydrogenase (FLD) and formate dehydrogenase, also producing energy in the form of NADH. The dissimilative pathway has been described as an energy producing and a detoxifying route, but conclusive evidence has not been provided for this. In order to elucidate this theory, we generated mutants lacking the FLD activity (Δfld1) and used flux analysis to evaluate the metabolic impact of this disrupted pathway. Unexpectedly, we found that the specific growth rate of the Δfld1 strain was only slightly lower (92%) than the control. In contrast, the sensitivity to formaldehyde pulses (up to 8mM) was significantly higher in the Δfld1 mutant strain and was associated with a higher maintenance energy. In addition, the intracellular flux estimation revealed a high metabolic flexibility of K. phaffii in response to the disrupted pathway. Our results suggest that the role of the dissimilative pathway is mainly to protect the cells from the harmful effect of formaldehyde, as they were able to compensate for the energy provided from this pathway when disrupted.

Alginates are polymers used in the food and pharmaceutical industries as stabilizing, thickening, gel or film-forming agents. Food coatings formed from alginate have shown to have excellent properties such as flexibility and resistance to tearing. These polysaccharides are extracted from natural brown algae, but they can also be produced by a bio-process. One strategy to produce alginates is through the manipulation of the culture conditions during fermentation using Azotobacter vinelandii. This work proposes the development of a PI control strategy to improve the production of alginate from Azotobacter vinelandii in a laboratory bio-reactor scale.

Alginate is a biomaterial produced by Azotobacter vinelandii, a diazotroph that, under nitrogen-fixing conditions, can fix nitrogen under high oxygen levels. In A. vinelandii, alginate is synthesized from fructose-6P via synthesis of precursor, polymerization, and modification/exportation. Due to its viscosifying, gelling, and thickening characteristics, alginate is widely used in food, pharmaceutical, and cosmetical industries. This study aimed to develop a continuous bioprocess and a comparative analysis of alginate production under diazotrophic and nondiazotrophic conditions. Continuous cultures were developed at three dilution rates (0.06, 0.08 and 0.10 h⁻¹). In steady state, the respiratory activity, alginate production, alginate molecular weight and the genes encoding alginate polymerase were determined. Under the conditions studied, the specific oxygen uptake rate and respiratory quotient were similar. The diazotrophic conditions improved the conversion of sucrose to alginate and the specific productivity rate, which was 0.24 ± 0.03 g g⁻¹ h⁻¹. A higher alginate molecular weight (725 ± 20 kDa) was also achieved under diazotrophic conditions, which can be explained by an increase in the gene expression of genes alg8 and alg44 (encoding polymerase). The results of this work show the feasibility of enhancing alginate production (yields and specific productivity rates) and quality (molecular weight) under nitrogen-fixing conditions, opening the possibility of developing a continuous bioprocess to produce alginate with specific characteristics under conditions of diazotrophy.

Hydrogels are gaining prominence in sustainable agriculture due to their water-retention capacity, biocompatibility, and tunable physicochemical behavior. Among natural polymers, alginate is particularly attractive because it forms hydrogels under mild conditions and provides a versatile platform for controlled release, soil conditioning, and environmental remediation. This review integrates advances in alginate-based hydrogel technologies from 2001 to 2024 through a combined bibliometric and patentometric analysis. A total of 266 scientific articles and 460 patent families were identified, revealing sustained growth in both research output and technological development. Encapsulation and controlled-release systems dominate the landscape, followed by soil and water treatment applications, while postharvest preservation, in vitro cultivation, and biodegradable packaging emerge as expanding areas. Overall, alginate-based hydrogels represent a multifunctional, biodegradable platform supporting precision agriculture and sustainable production systems within a circular bioeconomy framework.