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As the world population continues to grow, alternative protein sources must be sought to meet increased protein needs and avoid the detrimental effects of traditional protein production. Microbial proteins (MP) are a low-carbon footprint alternative suitable for manufacturing food and feed. Bacterial-based MP can be produced at moderate costs using agro-waste, which is already utilised by anaerobic digestion (AD) plants to produce biogas and fertilisers. At present, there is the opportunity to turn existing AD plants into biorefineries for bio-based products like MP destined for fish feed. In this work, we evaluated the feasibility of biogas production coupled with MP production in the same medium-sized European biogas plant through mass and energy balances and basic economic assessment. The liquid phase rich in volatile fatty acids resulting from agro-waste fermentation was used to obtain MP by mixed cultures in a continuous stirred tank reactor, with the highest VSS productivity (1.21 g/L day) obtained at hydraulic retention times of 2–3 days. The obtained MPs were rich in proteins (74.0% of TVS), PHAs (22.5%) and essential amino acids, useable as feed ingredients in aquaculture. An initial economic analysis showed that the production of 590 tMP/year could yield a break-even price of 1300 €/t of MP, taking into account the investments in the new technology and additional operating costs. This analysis illustrates the competitiveness of a combined plant when evaluated against established market benchmarks and highlights a promising prospect for the expansion of MP production capacity. [Display omitted] • MP were produced in a bioreactor with a maximum productivity of 1.21 g/L day. • MP were rich in proteins (74%), polyhydroxyalkanoates (22.5%), essential amino acids. • Plants for biogas production could be upgraded to produce MP for aquaculture. • The calculated break-even point for combined MP-biogas plants is 1300 €/t for MP. • A medium-sized biogas plant has the potential to host cost-competitive MP production. [ABSTRACT FROM AUTHOR]

Background: Shipworms are marine xylophagus bivalve molluscs, which can live on a diet solely of wood due to their ability to produce plant cell wall-degrading enzymes. Bacterial carbohydrate-active enzymes (CAZymes), synthesised by endosymbionts living in specialised shipworm cells called bacteriocytes and located in the animal's gills, play an important role in wood digestion in shipworms. However, the main site of lignocellulose digestion within these wood-boring molluscs, which contains both endogenous lignocellulolytic enzymes and prokaryotic enzymes, is the caecum, and the mechanism by which bacterial enzymes reach the distant caecum lumen has remained so far mysterious. Here, we provide a characterisation of the path through which bacterial CAZymes produced in the gills of the shipworm Lyrodus pedicellatus reach the distant caecum to contribute to the digestion of wood. Results: Through a combination of transcriptomics, proteomics, X-ray microtomography, electron microscopy studies and in vitro biochemical characterisation, we show that wood-digesting enzymes produced by symbiotic bacteria are localised not only in the gills, but also in the lumen of the food groove, a stream of mucus secreted by gill cells that carries food particles trapped by filter feeding to the mouth. Bacterial CAZymes are also present in the crystalline style and in the caecum of their shipworm host, suggesting a unique pathway by which enzymes involved in a symbiotic interaction are transported to their site of action. Finally, we characterise in vitro four new bacterial glycosyl hydrolases and a lytic polysaccharide monooxygenase identified in our transcriptomic and proteomic analyses as some of the major bacterial enzymes involved in this unusual biological system. Conclusion: Based on our data, we propose that bacteria and their enzymes are transported from the gills along the food groove to the shipworm's mouth and digestive tract, where they aid in wood digestion. [ABSTRACT FROM AUTHOR]

The current trend of increasing human population means that alternative protein sources need to be sought to avoid malnutrition. Fish is the most efficient protein-rich food, but aquaculture relies on fishmeal, whose production is environmentally unsustainable. In this study we evaluated the nutritional value of bacterial biomass produced by the biological conversion of zootechnical residues, for its use as feed in aquaculture. A bioreactor was fed with the fluid produced by the fermentation of zootechnical residues. Polyhydroxyalkanoates-producing microbial cultures were used to produce a biomass rich in proteins (61.8% of dry biomass) and amino acids, with glutamic (12.2% of total protein) and aspartic acid (8.7%) and the essential amino acids lysine (6.6%) and leucine (5.3%) being the most abundant. Feeding trials performed on Zebrafish revealed that the microbial proteins produced are a suitable alternative to the commercially available feed, with fish showing survival rates (74%) comparable to the control feed (82%), and even better results when enriched with oils and polyhydroxyalkanoates (96%). The results showed that it is possible to valorise agricultural residues into fish feed via biological conversion by polyhydroxyalkanoates-producing bacteria, while eliminating waste and producing biogas at the same time. [Display omitted] • Alternative protein sources are needed to avoid malnutrition due to population increase. • Agricultural and animal residues were upgraded into fish feed for aquaculture. • The obtained microbial biomass resulted rich in proteins and essential amino acids. • Fish feeding trials showed normal to improved survival rates and morphological traits. • Biological conversion of leftovers into fish feed is part of the circular bioeconomy. [ABSTRACT FROM AUTHOR]

Lignocellulose forms the structural framework of woody plant biomass and represents the most abundant carbon source in the biosphere. Turnover of woody biomass is a critical component of the global carbon cycle, and the enzymes involved are of increasing industrial importance as industry moves away from fossil fuels to renewable carbon resources. Shipworms are marine bivalve molluscs that digest wood and play a key role in global carbon cycling by processing plant biomass in the oceans. Previous studies suggest that wood digestion in shipworms is dominated by enzymes produced by endosymbiotic bacteria found in the animal’s gills, while little is known about the identity and function of endogenous enzymes produced by shipworms. Using a combination of meta-transcriptomic, proteomic, imaging and biochemical analyses, we reveal a complex digestive system dominated by uncharacterized enzymes that are secreted by a specialized digestive gland and that accumulate in the cecum, where wood digestion occurs. Using a combination of transcriptomics, proteomics, and microscopy, we show that the digestive proteome of the shipworm Lyrodus pedicellatus is mostly composed of enzymes produced by the animal itself, with a small but significant contribution from symbiotic bacteria. The digestive proteome is dominated by a novel 300 kDa multi-domain glycoside hydrolase that functions in the hydrolysis of β-1,4-glucans, the most abundant polymers in wood. These studies allow an unprecedented level of insight into an unusual and ecologically important process for wood recycling in the marine environment, and open up new biotechnological opportunities in the mobilization of sugars from lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

The article presents a study which investigated long-distance matches of bottlenose dolphins in Donegal Bay, Galway bay and Clew Bay in Ireland using photograph-identification catalogues. It is stated that dolphins from around the Irish coastal waters must be considered highly mobile and transient to relate its implications for the conservation and management of the species. The authors concluded that the resighting rate is high given that the sample size of individual bottlenose dolphins was relatively small.