Abstract
Rapid deterioration of harvested macroalgal biomass is a challenge for macroalgal industry and can be overcome with the inexpensive ensiling preservation. To improve silage quality, Saccharina latissima and Alaria esculenta biomass was subjected to ensiling conditions following a 2 × 4 factorial design, with 2 prewilting treatments (no-prewilting and prewilted to 300 g DM kg−1 fresh biomass) and 4 additive treatments (no additive, formic acid, single and two species of Lactobacillus inoculant), and ensiled for 3 or 12 months at 15 °C. Acetate was the main fermentation product in these seaweed silages. Prewilting reduced the acetate, mannitol, and NH3 content in silages. In S. latissima silages without additives, prewilting led to less acidification (pH = 5.7). Also, prewilting caused protein and phlorotannin degradation. When treated with formic acid, the silage pH was below 4 regardless of the biomass’s moisture content. The use of Lactobacillus spp. inoculants was essential for lactate production in seaweed silages, and it significantly lowered silage pH in S. latissima and prewilted A. esculenta compared to silages with no additives. A high level of the phlorotannin content was preserved (> 90%) in the 3-month A. esculenta silages without prewilting. However, major reduction of antioxidant activity was observed in 12-month silages in both seaweed species. In conclusion, ensiling is a viable method for preserving Alaria and Saccharina biomass. Prewilting restricted silage fermentation, and both formic acid and bacterial additives facilitated silage acidification. However, there was no clear benefit of these treatments in preserving the antioxidant activity.
Highlights
Brown marine macroalgae or seaweeds are characterized by their fast growth and their high contents in carbohydrates, minerals, and phlorotannin, which are1 3 Vol.:(0123456789)Journal of Applied Phycology t fresh biomass per hectare per year (Broch et al 2019; Fiskeridirektoratet 2020)
The triplicates from each ensiling treatments in the original design were pooled into one sample for chemical composition analysis, and the results shown in Table 4 were the average of 2 samples, replicates resulting from the omitted factor of chopping time
The chemical composition was measured to estimate the level of fiber, protein (N), carbohydrate, and ash content in the silages as essential parameters to evaluate for ruminant feed application
Summary
Brown marine macroalgae or seaweeds are characterized by their fast growth and their high contents in carbohydrates (e.g., alginate), minerals, and phlorotannin, which are1 3 Vol.:(0123456789)Journal of Applied Phycology t fresh biomass per hectare per year (Broch et al 2019; Fiskeridirektoratet 2020). Brown marine macroalgae or seaweeds are characterized by their fast growth and their high contents in carbohydrates (e.g., alginate), minerals, and phlorotannin, which are. The rapid post-harvest deterioration of macroalgal biomass is a known limitation to its further utilization as nutrients and bioactive ingredients. The freshly harvested biomass is preserved by anerobic fermentation in which epiphytic lactic acid bacteria (LAB) convert sugars into lactate (pKa of 3.86) and decrease the pH. The increased acidity and osmotic pressure arrest the microbial activities, and the nutrient content is preserved. Ensiling requires low mechanical and energy inputs. This is of great advantage for the preservation of harvested seaweeds in countries with climate conditions unfavorable for sun-drying and high labor costs (e.g., Norway). Ensiling potentially enables a year-round supply with biomass, batch process, and the possibility to avoid drying in several downstream processes which are designed to use wet biomass (Alvarado-Morales et al 2013; Bach et al 2014)
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