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In the fermentation and bioenergy industry, terrestrial biomass is usually fractionated and the collected components, such as starch, are processed separately. Such a separation has not been reported for seaweeds. In this work, the direct hydrothermal processing of the whole green seaweed Ulva sp. biomass is compared to processing of separated starch and cellulose, to find the preferable route for monosaccharide, hydrochar, and polyhydroxyalkanoates (PHA) production. Glucose was the major released monosaccharide. A significant share of the glucose yield comes from the starch fraction. The highest hydrochar yield with the lowest ash content was obtained from the separated cellulose fraction. The highest PHA yield was obtained using a whole Ulva sp. hydrolysate fermentation with Haloferaxmediterranei. Economic analysis shows the advantage of direct Ulva sp. biomass fermentation to PHA. The co-production of glucose and hydrochar does not add significant economic benefits to the process under plausible prices of the two outputs., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Offshore macroalgae biomass production is a promising, yet challenging, pathway to provide feedstock for biorefineries. In this work, a device and a process for dewatering offshore grown biomass of the green macroalgae Ulva sp. using high-voltage pulsed electric fields (PEF) was developed. Ulva sp. was cultivated attached to fish cages 15 km offshore. Increasing the applied voltage from 250 V to 500 V and invested PEF energy from 9.3 ± 0.4 J g -1  FW to 54.6 ± 0.2Jg -1  FW increased the extracted water from 0.033 ± 0.006 g Water g -1  FW to 0.150 ± 0.031 g Water g -1 FW. The energy consumption to achieve similar moisture content with air convection drying was lower by 78.73 ± 10.41 (JgFW -1 ) for 250 V and 339.31 ± 48.01 (JgFW -1 ) for 500 V, pulse duration 50 µs, pulse number 50, pulse repetition frequency 3 Hz. PEF leads to biomass compression of 8.45 ± 1.72% for 250 V protocol and 25.66 ± 2.53% for 500 V protocol. In addition, PEF leads to the reduction of water diffusivity of 18-19% in the treated biomass, reducing air drying kinetics., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Subcritical water hydrolysis and carbonization of the biomass are an emerging green technology for seaweed biomass processing. In this work, a novel approach for co-generation of two energy streams from seaweed biomass (fermentable sugars and solid hydrochar) with subcritical water from a green macroalgae Ulva sp. was developed. It was found that for the released of glucose, xylose, rhamnose, fructose, and galactose, the process temperature is the most significant parameter, followed by salinity, solid load, and treatment time. For the formation of fermentation inhibitor 5-hydroxymethylfurfural (5-HMF), temperature also was the most important parameter, followed by residence time, salinity, and solid load. The optimum parameters for maximal release of total sugars under minimum formation of 5-HMF were 170 °C (800 kPa abs.), 5% solid loading, 40 min residence time, and 100% salinity. The hydrochar yield was 19.4% and hydrochar high heating value was 20.2 ± 1.31 MJ kg−1. These results provide new detailed information on the subcritical hydrolysis and carbonization of Ulva sp. biomass and show co-production of fermentable monosaccharides and hydrochar. [ABSTRACT FROM AUTHOR]

Edible green marine macroalgae, especially species of Ulva , can accumulate starch up to 30% of their dry weight; however, its physicochemical, functional, and digestibility properties are still unknown. In this study, we characterized molecular mass distribution, amylose-amylopectin ratio, crystallinity, hydration capacity, viscoelastic and pasting properties, and the digestibility of starch extracted from Ulva ohnoi and compared it to rice and potato starches. Ulva starch had a higher amylose content than rice and potato starches (55.0%, 34.5% and 24.3%, respectively). Ulva starch exhibited higher hydration capacity than rice starch (25.7 g water /g starch and 10.3 g water /g starch respectively), while potato starch exhibited the highest hydration capacity, of 41 g water /g starch , probably mainly due to presence of phosphate groups. Ulva starch had the lowest mass-average molecular weight ((1.17×106 g/mol), compared to rice (4.40×106 g/mol) and potato (5.80×106 g/mol) starches. Ulva starch exhibited the highest G′ and viscosity setback ratio after cooling-induced gelation following gelatinization, probably thanks to its uniquely high amylose content, which led to higher tendency for physical crosslinking by retrogradation. This may also explain the fact that Ulva starch exhibited somewhat lower digestibility after retrogradation, compared to rice and potato starches, which would be advantageous for forming resistant starch serving as a dietary fiber, and lowering glycemic index. The superior gel properties on the one hand and lower digestibility, which would be helpful in tackling obesity & diabetes, on the other hand, make U lva starch a unique and promising new functional food ingredient. [Display omitted] • Ulva ohnoi amylose content: 55% of the starch, more than most terrestrial starches. • Ulva starch exhibited higher hydration capacity than rice starch. • Gelatinized Ulva starch exhibited the highest G′ after cooling-induced gelation. • Ulva starch had somewhat lower digestibility than rice and potato starches. • Lower digestibility may lead to lower glycemic index, advantageous against diabetes. [ABSTRACT FROM AUTHOR]