The growing aquaculture industry has an increasing demand for novel, sustainably produced protein sources for aquafeed. This study aimed to determine the apparent digestibility (AD%), pellet quality, and protein score of four novel fungal proteins in rainbow trout (Oncorhynchus mykiss), namely, PEKILO® (PEK) derived from Paecilomyces variotii, Aspergillus oryzae (AO), Rhizopus oligosporus (RO), and Rhizopus delemar (RD). All fungi were grown on various side-streams, such as beet vinasse, thin stillage, and whole stillage. The diets were produced by extrusion technology and consisted of control and test diets with a 30:70 test ingredient/control ratio. Feeding lasted for 39 days. Each tank had 20 fish, with three replicates per dietary treatment. One-way ANOVA was performed to compare the means of the groups with each other. The dry matter (DM) digestibility of PEK was significantly higher than that of AO, RD, and RO, all with similar digestibility. The crude protein AD% for PEK was 86.5%, which is significantly higher than that of the other fungal sources. AO, PEK, RD, and RO had similar crude fat AD% compared to each other, at 83.8%, 87.4%, 90.5%, and 88.5%, respectively. The pellet quality was found to deteriorate with addition of fungal proteins. PEK had high AD% for most of the macronutrients tested and better pellet quality. © 2025 by the authors.

Limited feed ingredients hinder aquaculture’s rapid growth. Current unsustainable fish feeding practices use ingredients like fishmeal and soybean meal, which could be directly consumed for as human food. This demands novel alternatives for fish nutrition. While studies have explored plant/animal-based protein sources, they have not fully met fish feed nutritional needs. Single-cell proteins like bacteria, algae, and fungi are gaining attention as sustainable alternatives to traditional fish feed protein sources. Filamentous fungal biomass stands out with its high protein content, essential amino acids, and functional amino acids like lysine and arginine. This biomass also provides other nutrients that fish commonly require, such as essential fatty acids (linoleic acid, linolenic acid, arachidonic acid), minerals (phosphorus, potassium, calcium), vitamins (B, C, E), and pigments. Incorporating cell wall components like chitin, chitosan, and beta-glucans makes fungal biomass a functional feed ingredient that enhances fish immune systems. When applied to rainbow trout diets, fungal-based feed is highly digestible, comparable to fishmeal-based feed, and positively impacts gut microbiomes. The increase of lactic acid bacteria (Lactococcus lactis) after consuming fungal-based feed suggests its potential as a fish feed prebiotic. 

While fungal biomass holds promise as a nutrient-rich fish feed source, its large-scale production on synthetic substrates poses economic challenges. To optimize production, organic-rich waste like Distiller's Dried Grains with Solubles (DDGS) and thin stillage from ethanol production are explored as substrates. Thin stillage, previously considered for fungal biomass production, faces difficulties due to its high solid content. Optimizing thin stillage's suspended solids for cultivating different filamentous fungi from Ascomycetes and Zygomycetes is necessary. Submerged cultivation of Aspergillus oryzae, Rhizopus delemar, and Neurospora intermedia was tested using various thin stillage dilutions. Cultivating these species in 75% diluted thin stillage yielded the highest biomass. The harvested fungal biomass contained around 50% protein and 45% essential amino acids, with ash content below 10%, enhancing fish digestibility. Notably, when 75% diluted thin stillage was used, the washing step could be skipped without compromising final biomass quality, streamlining production processes. Using fungal-based feed in fish nutrition presents a sustainable alternative to traditional fishmeal-based feed. It goes beyond protein and amino acids, providing other essential nutrients such as fatty acids, minerals, pigments etc. High digestibility and positive effects on fish health through gut microbiome modulation make it a valuable substitute for common protein sources. To enhance sustainability, scaling up fungal biomass production using diluted thin stillage as a substrate is a promising avenue. 

Thin stillage holds promise as a substrate for cultivating filamentous fungi. The suspended solids content of thin stillage directly influences biomass production. However, little attention has been given to its effects on fungal cultivation and composition, which is the focus of the current study. Various thin stillage dilutions were used to cultivate Zygomycete and Ascomycetes. Biomass and nutrient uptake were monitored during the cultivation. The harvested biomass was analyzed to assess nutrient composition in relation to fish dietary requirements. Thin stillage diluted to 75 % significantly enhanced fungal biomass production, with increases of 160 %, 213 %, and 235 % for A. oryzae, R. delemar, and N. intermedia, respectively. The harvested fungal biomass boasted approximately 50 % protein content, constituting 45 % essential amino acids. These findings underscore the potential of cultivating fungi in diluted thin stillage to boost biomass production and its high-quality nutritional composition positions it as a valuable candidate for fish feed formulations.

Changes in gut microbial composition over time in rainbow trout fed differentially processed diets supplemented with the filamentous fungi Neurospora intermedia were investigated in a 30-day feeding trial. Fish were fed a reference diet, non-preconditioned diet (NPD), or preconditioned (heat-treated) diet (PD), with the same inclusion level of N. intermedia in diets NPD and PD. Gut microbiota were analyzed on day 0, 10, 20, and 30. Gut microbial composition was similar for all diets on day 0, but was significantly different at day 10 and day 20. On day 30, the gut again contained similar communities irrespective of diet. The overall gut microbiota for each diet changed over time. Abundance of Peptostreptococcus and Streptococcus was higher in the initial days of feeding in fish fed on commercial diet, while a significant increase in lactic acid bacteria (Lactococcus lactis) was observed on day 30. Feed processing (preconditioning) did not contribute largely in shaping the gut microbiome. These results indicate that dietary manipulation and duration of feeding should be considered when evaluating gut microbial composition in cultured fish. A minimum 30-day feeding trial is suggested for gut microbiome, host and diet interaction studies. Copyright © 2021 Singh, Karimi, Vidakovic, Dicksved, Langeland, Ferreira, Taherzadeh, Kiessling and Lundh.

Cellulosic biomass has been widely used as a feedstock for biofuel applications due to its low-cost, renewability and abundance. However, the production of liquid biofuels is still costly and inefficient mainly due to the recalcitrant structure of lignocellulosic biomass. It requires expensive pretreatment methods to break down the plant cell wall, and efficient enzymes capable of hydrolysing cellulose into glucose. One possible solution to make bioethanol production cost-effective and, at the same time, increase the energy output from the biomass is genetic engineering. Genetic modification has been reported as an effective strategy to increase productivity, biomass yields and specific traits of various agricultural plants. This paper provides an overview of the potential of cereal-based agricultural waste as a feedstock for bioethanol production. It focuses on the progress of different techniques used in genetic modification (transgenesis, cisgenesis mutagenesis and conventional breeding) to genetically engineer plant cell wall. Utilization of genetic modification of cereal plants is proposed as a solution to high costs and low yields of bioethanol production from cereal-based agricultural waste.

The rapid growth of aquaculture and scarcity of conventional fish feed supplements has prompted the introduction of new sustainable supplementation sources. In this study, the potential of five strains of fungal biomass of Ascomycetes and Zygomycetes edible filamentous fungi, Aspergillus oryzae, Neurospora intermedia, Rizhopus oryzae, Monascus purpureus, and Fusarium venenatum, cultivated on vinasse, a by-product of the bioethanol industry, as alternative protein sources for fishmeal in the fish diet was evaluated. It was observed that 5% vinasse with an initial pH of 5-6.5 can support fungal biomass yields of 34.3 +/- 2.4-118.5 +/- 3.9 g DM/L for A. Oryzae, N. intermedia, and R. oryzae. High protein contents of about 44.7%, 57.6%, and 50.9% (w/w), and fat contents of 7.0%, 3.5%, and 5.5% (w/w) were obtained for A. oryzae, N. intermedia, and R. oryzae, respectively. The latter three fungi species contained noticeable amino acid contents, including promising profiles of amino acids that are highly compatible with those of fishmeal. These findings provide evidence that fungal biomasses, with their relatively high protein content, good amino acid profiles, and other essential nutrients, are a promising supplementation alternative that can be produced from low-value by-products and organic-rich waste streams like vinasse to meet the dietary protein requirements in fish feed.

Organic-rich waste and industrial by-product streams, generated in enormous amounts on a daily basis, contain substantial amounts of nutrients that are worthy of recovery. Biological conversion of organic-waste streams using filamentous fungi is a promising approach to convert nutrients into value-added bioproducts, such as fungal biomass. High-protein fungal biomass contains different kinds and levels of amino acids, fatty acids, immunostimulants, antioxidants, pigments, etc., which make it a potential choice for application in animal feed supplementation. Considering the challenges long faced by the aquaculture industry in fishmeal production due to the increasing prices and environmental concerns, the aquaculture industry is forced to provide alternative protein-rich sources to replace conventional fishmeal. In this review, the possibilities of utilization of filamentous fungi biomass cultivated on organic-rich waste streams, as an alternative nutrient source in fish feed, were thoroughly reviewed.