Thermobia domestica belongs to an ancient group of insects and has a remarkable ability to digest crystalline cellulose without microbial assistance. By investigating the digestive proteome of ...Thermobia, we have identified over 20 members of an uncharacterized family of lytic polysaccharide monooxygenases (LPMOs). We show that this LPMO family spans across several clades of the Tree of Life, is of ancient origin, and was recruited by early arthropods with possible roles in remodeling endogenous chitin scaffolds during development and metamorphosis. Based on our in-depth characterization of Thermobia's LPMOs, we propose that diversification of these enzymes toward cellulose digestion might have endowed ancestral insects with an effective biochemical apparatus for biomass degradation, allowing the early colonization of land during the Paleozoic Era. The vital role of LPMOs in modern agricultural pests and disease vectors offers new opportunities to help tackle global challenges in food security and the control of infectious diseases.
The growing world population will comprise 9 billion people by 2050 and protein consumption will be 50% higher in 2030 compared to 2000. To prepare for this increase, new sources of protein must be ...sought to replace the non-environmentally sustainable animal and plant proteins that are currently produced. Insects or microbial proteins can indeed be an economic and nutritious alternative not only for animal feed, but also as supplements for human consumption. Our study aimed at assessing the production of microbial proteins destined to aquaculture feed, using as starting material agricultural and animal wastes, in order to tackle at the same time the problem of waste disposal. A bioreactor was feed with the fluid obtained from the acidogenic fermentation of zootechnical and agricultural waste, containing a mixture of VFAs of which acetic acid was the most abundant (43.8 %). The highest productivity (1.6-2.0 gMLVSS/L per day) was obtained with an HRT of 2 days and an ORL of 22 gCOD/L per day. The produced bacterial biomass was analyzed to determine its suitability as fish feed, showing a crude protein content of 73 % over the MLVSS, of which glutamic and aspartic acid were the most abundant. These amounts are higher than what is found in most commercial fish feeds, suggesting that the bacterial biomass has potential to be used as aquaculture feed. PHAs accumulation tests on part of the biomass recovered from the bioreactor showed concentration of PHAs up to 62.2 % over cell dry weight, a positive result since PHAs have the potential to enhance fish growth.
Woody (lignocellulosic) plant biomass is an abundant renewable feedstock, rich in polysaccharides that are bound into an insoluble fiber composite with lignin. Marine crustacean woodborers of the ...genus Limnoria are among the few animals that can survive on a diet of this recalcitrant material without relying on gut resident microbiota. Analysis of fecal pellets revealed that Limnoria targets hexose-containing polysaccharides (mainly cellulose, and also glucomannans), corresponding with the abundance of cellulases in their digestive system, but xylans and lignin are largely unconsumed. We show that the limnoriid respiratory protein, hemocyanin, is abundant in the hindgut where wood is digested, that incubation of wood with hemocyanin markedly enhances its digestibility by cellulases, and that it modifies lignin. We propose that this activity of hemocyanins is instrumental to the ability of Limnoria to feed on wood in the absence of gut symbionts. These findings may hold potential for innovations in lignocellulose biorefining.
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.
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.
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.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PHAs produced from biowaste are an ecological alternative to petroleum-based plastics. Despite their advantageous characteristics, their commercialisation is limited because the extraction process is ...still inefficient. This review describes approaches applied to PHA-rich biomass to recover bio-based products beyond their valorisation as bioplastics. The whole PHA-containing microbial cell can be used for animal feed, since PHAs can boost the immune system of the fed animals, and direct extrusion of PHA-rich biomass allows the production of biocomposites. After PHAs extraction, by-products can be recovered to make high-value products such as animal feed, biostimulants, protein hydrolysates, flocculants, adhesives and pharmaceutical. PHAs-rich microbes can also be fed to animals able to excrete PHAs in their faecal pellets, from which they can be easily retrieved. Such approaches have the potential to favour the transition to bioplastics obtained from biowaste streams, thus reducing the environmental impact of plastic production.
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•The diffusion of PHA-based bioplastics is hindered by its high production costs.•PHA-rich biomass can be valorised beyond its use as bioplastic.•PHA-rich whole cells can be used to produce animal feed and biocomposites.•PHA-extractions by-products can be recycled to manufacture high-value products.•Biological extraction methods allow an easier and greener recovery of PHAs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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•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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The use of petroleum-based plastic has led to its accumulation in the environment, with negative impacts on the ecosystem and the biota. Polyhydroxyalkanoates (PHAs), biobased and biodegradable ...plastics produced by microbes, have many commercial applications, however their high production cost means they cannot yet compete with traditional plastics. At the same time, the problem of the growing human population implies that improved crop production is needed to avoid malnutrition. Biostimulants enhance plant growth and have the potential to improve agricultural yields; they can be obtained from biological feedstock, including microbes. Therefore, there is scope for coupling the production of PHAs with that of biostimulants, making the process more cost-efficient and minimizing by-products generation. In this work, low-value agro-zoological residues were processed to obtain PHA-storing bacteria via acidogenic fermentation; PHAs destined for the bioplastic market were extracted, and the protein-rich by-products were turned into protein hydrolysates using different treatment methods, assessing their biostimulant effects in growth trials with tomato and cucumber plants. The results indicate that the best hydrolysis treatment, realizing the highest amount of organic nitrogen (6.8 gN-org/L) while achieving the best PHA recovery (63.2 % gPHA/gTS), is obtained with strong acids. All the protein hydrolysates were effective in improving either roots or leaf development, with various results, depending on the species and the growth method. The acid hydrolysate was the most effective treatment to enhance the development of shoots (21 % increase compared to the control) and roots (16 % increase for the dry weight and 17 % for main root length) of hydroponically-grown cucumber plants, while pot-grown tomatoes, biostimulated via foliar spray, developed bigger shoots (up to 41 %) with the hydrolysate obtained from the alkaline treatment. These preliminary results indicate that simultaneous production of PHAs and biostimulants is feasible, and that commercialization could be achievable given the expected reduction in production costs.
The dashed lines represent phases of the overall experimental set-up which were not tested within this work, which are however foreseen outcomes of the described pathways. PHAs = polyhydroxyalkanoates. Display omitted
•Low-value zoological residues were turned into PHA-rich bacteria by fermentation.•PHAs were extracted with a recovery rate of 63.2 % gPHA/gTS using acid treatments.•Protein-rich by-products from the extraction were turned into protein hydrolysates.•Protein hydrolysates showed biostimulatory effects on tomato and cucumber plants.•Tomatoes developed shoots 41 % bigger than the control with the alkaline hydrolysate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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•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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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
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.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Unconventional protein sources are necessary to tackle the increasing demand for food. Microbial proteins (MP) are an alternative source of proteins for feed or food, suitable as feed for ...aquaculture. Substituting fishmeal with MP obtained from agricultural wastes could reduce the environmental burden of aquaculture and help with waste management. In this study, pure culture MP from the PHA-producer Thauera sp. Sel9 were obtained from agricultural residues (agro-zootechnical digestate and pasta industry leftovers). The produced MP was used in feeding tests with the model fish zebrafish (Danio rerio) to assess potential toxic effects and evaluate overall fish health. The obtained MP was rich in protein (59.5 % w/w over TS) and PHAs (15.0 %) and comprised all fish essential amino acids. The chemical scores and essential amino acid index confirmed the excellent quality of the MP. The feeding tests with 50 % feed substitution with MP resulted in survival rates (80–88 %) comparable to the control group (78 %), with only 100 % MP showing increased mortality. Thauera MP obtained from agricultural residues has the potential to become a partial fishmeal substitute in fish-farming.
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•Pure culture Thauera sp. Sel9 microbial proteins were produced from agro-residues.•The MP was rich in protein (59.5 %), PHAs (15.0 %), and fish essential amino acids.•Feeding trials with zebrafish were performed to assess potential use in aquaculture.•50 % feed replacement showed survival rates (80–88 %) similar to the control (78 %).•Thauera MP has the potential to become a partial fishmeal substitute in fish-farming.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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