Tailoring regulatory components for metabolic engineering in cyanobacteria.

The looming climate crisis has prompted an ever-growing interest in cyanobacteria due to their potential as sustainable production platforms for the synthesis of energy carriers and value-added chemicals from CO2 and sunlight. Nonetheless, cyanobacteria are yet to compete with heterotrophic systems in terms of space-time yields and consequently production costs. One major drawback leading to the low production performance observed in cyanobacteria is the limited ability to utilize the full capacity of the photosynthetic apparatus and its associated systems, i.e. CO2 fixation and the directly connected metabolism. In this review, novel insights into various levels of metabolic regulation of cyanobacteria are discussed, including the potential of targeting these regulatory mechanisms to create a chassis with a phenotype favorable for photoautotrophic production. Compared to conventional metabolic engineering approaches, minor perturbations of regulatory mechanisms can have wide-ranging effects.

Protein blends and extrusion processing to improve the nutritional quality of plant proteins.

Plant proteins have low protein nutritional quality due to their unbalanced indispensable amino acid (IAA) profile and the presence of antinutritional factors (ANFs) that limit protein digestibility. The blending of pulses with cereals/pseudocereals can ensure a complete protein source of IAA. In addition, extrusion may be an effective way to reduce ANFs and improve protein digestibility. Thereby, we aimed to improve the protein nutritional quality of plant protein ingredients by blending different protein sources and applying extrusion processing. Protein blends were prepared with pea, faba bean, quinoa, hemp, and/or oat concentrates or flours, and extrudates were prepared either rich in pulses (texturized vegetable proteins, TVPs) or rich in cereals (referred to here as Snacks). After extrusion, all samples showed a reduction in trypsin inhibitor activity (TIA) greater than 71%. Extrusion caused an increase in the total in vitro protein digestibility (IVPD) of TVPs, whereas no significant effect was shown for the snacks. According to the molecular weight distribution, TVPs presented protein aggregation. The results suggest that the positive effect of decreased TIA on IVPD is partially counteracted by the formation of aggregates during extrusion which restricts enzyme accessibility. After extrusion, all snacks retained a balanced amino acid score whereas a small loss of methionine + cysteine was observed in the TVPs, resulting in a small reduction in IAA content. Thus, extrusion has the potential to improve the nutritional quality of TVPs by reducing TIA and increasing protein digestibility.

Fast peroxydisulfate oxidation of the antibiotic norfloxacin catalyzed by cyanobacterial biochar.

Peroxydisulfate (PDS) is a common oxidant for organic contaminant remediation. PDS is typically activated by metal catalysts to generate reactive radicals. Unfortunately, as radicals are non-selective and metal catalysts may cause secondary contamination, alternative selective non-radical pathways and non-metal catalysts need attention. Here we investigated PDS oxidation of commonly detected antibiotic Norfloxacin (NOR) using cyanobacterial nitrogen rich biochars (CBs) as catalysts. NOR was fully degraded by CB pyrolysed at 950 °C (CB950) within 120 min. CB950 caused threefold faster degradation than low pyrolysis temperature (PT) CBs and achieved a maximum surface area normalized rate constant of 4.38 × 10-2 min-1 m-2 L compared to widely used metal catalysts. CB950 maintained full reactivity after four repeated uses. High defluorination (82%) and mineralization (>82%) were observed for CB950/PDS. CBs were active over a broad pH range (3-10), but with twice as high rates under alkaline compared with neutral conditions. NOR is degraded by organic, •OH and SO4•- radicals in low PT CBs/PDS systems, where the presence of MnII promotes radical generation. Electron transfer reactions with radicals supplemented dominate high PT CBs/PDS systems. This study demonstrates high PT biochars from algal bloom biomass may find use as catalysts for organic contaminant oxidation.