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Arthrospira maxima is a natural source of fine chemicals for multiple biotechnological applications. We determined the optimal environmental conditions for A. maxima by measuring its relative growth rate (RGR), pigment yield, and photosynthetic performance under different pH and temperature conditions. RGR was highest at pH 7–9 and 30 °C. Chlorophyll a, phycocyanin, maximal quantum yield (Fv/Fm), relative maximal electron transport rate (rETRmax), and effective quantum yield (ΦPSII) were highest at pH 7–8 and 25 °C. Interestingly, phycoerythrin and allophycocyanin content was highest at 15 °C, which may be the lowest optimum temperature reported for phycobiliprotein production in the Arthrospira species. A threestep purification of phycocyanin (PC) by ultrafiltration, ion-exchange chromatography, and gel filtration resulted in a 97.6% purity of PC.

Environmentally sound plant treatments that can impose mild physiological stress and elicit bioaccumulation of useful phytochemicals such as kaempferols are limited. We tested ABA foliar application, 100 or 200 µM, and two types of leaf wounding, piercing or hole punching in young greenhouse-grown soy plants. Leaf gas exchange and A/C i response, ΦPSII, pigments and antiradical activity were measured using the same leaf and kaempferols were measured in the leaf above. ABA 200 µM-treated plants had ≥ 20% less gas exchange and 17% less ETR, but greater V cmax and J max compared to control. They had 55% and 100% more stomatal limitation to P net and ΦPSII, respectively, than control. Leaf-wounded plants showed the lowest stomatal limitation to either P net or ΦPSII. Leaf piercing increased chlorophylls 39% and carotenoids 38% compared to control. Six kaempferols quantified were found to be mono-, di-and triglycosides. Each leaf treatment increased total kaempferol yield ranging from 42% in ABA 100 µM to 68% in ABA 200 µM treatment compared to control. In general, kaempferol yields were positively correlated to Pnet in ABA 100 µM-treated plants and to g s in ABA 200 µM-treated plants but negatively correlated to P net in leaf-pierced plants. ABA application and wounding affected the association between photosynthetic primary metabolism and kaempferol accumulation differently. Both ABA application and wounding are promising leaf treatments for eliciting kaempferol accumulation in young soy leaves.

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