Factors affecting the microbial digestion of an industrial seaweed-based residue

Abstract

Commercial preparation of a seaweed extract from the brown alga Ascophyllum nodosum for use as fertiliser and soil improver produces a sludge residue which requires remediation. This residue is rich in nutrients and offers the potential for other value-added products. The residue composition was analysed, a microbial digestion process for the residue was developed, and several factors affecting the digestion process were studied. The residue showed an alkaline pH (8.61±0.39) and 16% (w/w) total solids, which comprised 40.6% mineral, 29.5% fibre, 24.3% lipid, 4.9% protein and 0.5% polyphenols. The optimised digestion system included a 3-day anaerobic phase to decrease pH (from 8.96±0.40 to 7.72±0.38), the addition of an inoculum, followed by a 10-day aerobic phase where the insoluble material was digested. Every 3 days, the solubilised material was decanted and replaced with water to delay metabolite inhibition. The rate of digestion (decrease in insoluble material of 28.6±14.2% over 13 days) was influenced by the initial insoluble (R 2 00.773) and soluble (R 2 0 0.672) matter, the pH at the beginning of the aerobic phase (R 2 00.528) and by the accumulation of solubilised digestion products. A compositional analysis of the insoluble material after digestion showed that the lipid content of the residue was 96% digested and that the proportion of protein increased by 82.4%. Inocula and metabolite inhibition were critical features of A. nodosum residue digestion. Similar organic residues require a carefully chosen inoculum and a minimum initial insoluble content (65-70%) and/or a maximum soluble content (25.30%).

Optimisation of biogas generation from brown seaweed residues: Compositional and geographical parameters affecting the viability of a biorefinery concept

“…Also, biodegradability of biomass can be affected by several other factors like crystalline structure, the extent of cellulosic polymers, the surface properties of biomass, the amount of lignin content, the presence of hemicellulosic materials and the strength of fibers [44]. Other relevant studies were conducted on factors affecting the microbial digestion of an industrial seaweed-based residue of AN post alginate extraction [45,46]. The residue characterised by these showed an alkaline pH of the substrate prior to digestion and the authors identified that the digestibility was influenced by soluble/insoluble matter and inocula's metabolite inhibition, which are critical features for the digestion of the residues.…”

Leclercia adecarboxylata C12, The Newly Isolated Cellulose-degrading Bacteria from Indonesian Coffee Pulp

“…This newly isolated cellulose-degrading bacterium and its cellulase properties from the coffee pulp was novel research that had never been published before. Nevertheless, the cellulose-degrading capacity of Leclercia adecarboxylata has been indicated by other researchers (Nogales et al 2012;Yadav et al 2012).…”

Effects of kelp residues fermented with probiotics on the culture of sea cucumber,Apostichopus japonicus

“…Therefore, kelp residue had been usually added as accessory material in the feed for livestock farming and aquaculture such as for broiler chicken, Litopenaeus vannamei, and so on (Ahmed, Mun, Islam, & Yang, 2014;Martínez & Olvera, 2016;Peng, Chang, Ma, & Li, 2017). With the metabolic activity of microorganisms, the raw material of the feed is converted to small molecules such as peptides, amino acids and reducing sugars, resulting in more nutrient availability (Nogales, Concannon, & Hall, 2012). Therefore, the kelp residues appear to be viable as an effective sea cucumber feedstuff and can supplement the shortage of Sargassum thunbergii in the current sea cucumber feed industry.…”

“…Fermented feed is obtained by degrading material with appropriate microorganisms. With the metabolic activity of microorganisms, the raw material of the feed is converted to small molecules such as peptides, amino acids and reducing sugars, resulting in more nutrient availability (Nogales, Concannon, & Hall, 2012). The fermented feed has better palatability and is more easily digested and absorbed (Akinola, Onakomaiya, Agunbiade, & Oso, 2015;Alshelmani, Loh, Foo, Sazili, & Lau, 2016).…”