Current trends and possibilities of typical microbial protein production approaches: a review.

Global population growth and demographic restructuring are driving the food and agriculture sectors to provide greater quantities and varieties of food, of which protein resources are particularly important. Traditional animal-source proteins are becoming increasingly difficult to meet the demand of the current consumer market, and the search for alternative protein sources is urgent. Microbial proteins are biomass obtained from nonpathogenic single-celled organisms, such as bacteria, fungi, and microalgae. They contain large amounts of proteins and essential amino acids as well as a variety of other nutritive substances, which are considered to be promising sustainable alternatives to traditional proteins. In this review, typical approaches to microbial protein synthesis processes were highlighted and the characteristics and applications of different types of microbial proteins were described. Bacteria, fungi, and microalgae can be individually or co-cultured to obtain protein-rich biomass using starch-based raw materials, organic wastes, and one-carbon compounds as fermentation substrates. Microbial proteins have been gradually used in practical applications as foods, nutritional supplements, flavor modifiers, and animal feeds. However, further development and application of microbial proteins require more advanced biotechnological support, screening of good strains, and safety considerations. This review contributes to accelerating the practical application of microbial proteins as a promising alternative protein resource and provides a sustainable solution to the food crisis facing the world.

Effects of Garlic Oil and Cinnamaldehyde on Sheep Rumen Fermentation and Microbial Populations in Rusitec Fermenters in Two Different Sampling Periods.

Garlic oil (GO) and cinnamaldehyde (CIN) have shown potential to modify rumen fermentation. The aim of this study was to assess the effects of GO and CIN on rumen fermentation, microbial protein synthesis (MPS), and microbial populations in Rusitec fermenters fed a mixed diet (50:50 forage/concentrate), as well as whether these effects were maintained over time. Six fermenters were used in two 15-day incubation runs. Within each run, two fermenters received no additive, 180 mg/L of GO, or 180 mg/L of CIN. Rumen fermentation parameters were assessed in two periods (P1 and P2), and microbial populations were studied after each of these periods. Garlic oil reduced the acetate/propionate ratio and methane production (p < 0.001) in P1 and P2 and decreased protozoal DNA concentration and the relative abundance of fungi and archaea after P1 (p < 0.05). Cinnamaldehyde increased bacterial diversity (p < 0.01) and modified the structure of bacterial communities after P1, decreased bacterial DNA concentration after P2 (p < 0.05), and increased MPS (p < 0.001). The results of this study indicate that 180 mg/L of GO and CIN promoted a more efficient rumen fermentation and increased the protein supply to the animal, respectively, although an apparent adaptive response of microbial populations to GO was observed.

Impact of the environmental parameters on Single Cell Protein production and composition by Cupriavidus necator.

Due to the rapid increase in the world's population, many developing countries are facing malnutrition problems, including famine and food insecurity. Particularly, the deficiency of protein sources becomes a serious problem for human and animal nutrition. In this context, Single Cell Proteins, could be exploited as an alternative source of unconventional proteins. The aim of the study was to investigate SCP production and composition by Cupriavidus necator under various environmental conditions, temperature and pH values. A mono-factorial approach was implemented using batch bioreactor cultures under well-controlled conditions. Results were compared in terms of bacterial growth and SCP composition (proteins, nucleic acids, amino acids and elemental formula). Complementary analyses were performed by flow cytometry to study cell morphology, membrane permeability and the presence of Poly(3-hydroxybutyrate) (PHB) production. Our data confirmed the ability of C. necator to produce high amount of proteins (69% DW at 30°C and pH7). The results showed that temperature and pH independently impact SCP production and composition. This impact was particularly observed at the highest temperature (40°C) and also the lowest pH value (pH5) providing lower growth rates, cell elongation, changes in granularity and lower amounts of proteins (down to 44%DW at pH5) and nucleic acids. These low percentages were related to the production of PHB production (up to 44%DW at 40°C) which is the first report of a PHB accumulation in C. necator under nutrient unlimited conditions.

Evaluating the dose-dependent effects of curcumin nano-micelles on rumen fermentation, nitrogen metabolism, and nutrient digestibility in heat-stressed fattening lambs: Implications for climate change and sustainable animal production.

Global warming threatens livestock production, especially in hot climates. This study evaluated the dose-dependent impacts of dietary curcumin nano-micelles (CNM) on rumen fermentation, nitrogen metabolism, and nutrient digestibility in heat-stressed fattening lambs. Thirty-two crossbred male lambs [ˆIle-de-France × (Dalagh × Romanov)] were utilized within the current study. The initial weight of lambs was documented as averaged by 31.2 ± 1.55 kg, while they were in their 4th to 5th months of age. Animals were fed increasing doses of dietary CNM (0, 20, 40, and 80 mg/day) over 97 days, under severe heat stress conditions with average temperature-humidity index (THI) of 24.5. Quadratic improvements (p < 0.01) occurred in weight gain, average daily gain (ADG), and feed conversion ratio (FCR) by 28.7%, 27.4%, and 23.9%, respectively, in the T40 group compared to the control. Additionally, T40 increased fiber digestion by 2.8% (p < 0.05). Furthermore, T40 quadratically improved parameters of rumen fermentation, including concentrations of NH3-N (p < 0.05), total volatile fatty acids (TVFA; p < 0.01), acetate (p < 0.05), and iso-valerate (p < 0.05), by 13.9%, 12.5%, 15.0%, and 43.5%, respectively, compared to the control. Quadratic increases were also observed in nitrogen balance (p < 0.05) and microbial protein synthesis (p < 0.01) by 19.8% and 37.6%, respectively, in the T40 group. Quadratic models estimated optimal CNM levels between 41.5 and 48.6 mg/day for multiple parameters. These findings indicate CNM at dose level of 40 mg/day could benefit heat-stressed lambs through enhanced rumen function and microbiota. Further research should refine ideal dosing for various species and production phases as higher levels adversely impacted fiber digestibility. Overall, CNM shows promise as a sustainable nutritional intervention for livestock production facing global warming.

A comprehensive report on valorization of waste to single cell protein: strategies, challenges, and future prospects.

The food insecurity due to a vertical increase in the global population urgently demands substantial advancements in the agricultural sector and to identify sustainable affordable sources of nutrition, particularly proteins. Single-cell protein (SCP) has been revealed as the dried biomass of microorganisms such as algae, yeast, and bacteria cultivated in a controlled environment. Production of SCP is a promising alternative to conventional protein sources like soy and meat, due to quicker production, minimal land requirement, and flexibility to various climatic conditions. In addition to protein production, it also contributes to waste management by converting it into food and feed for both human and animal consumption. This article provides an overview of SCP production, including its benefits, safety, acceptability, and cost, as well as limitations that constrains its maximum use. Furthermore, this review criticizes the downstream processing of SCP, encompassing cell wall disruption, removal of nucleic acid, harvesting of biomass, drying, packaging, storage, and transportation. The potential applications of SCP, such as in food and feed as well as in the production of bioplastics, emulsifiers, and as flavoring agents for baked food, soup, and salad, are also discussed.

Evaluation of cell disruption methods for protein and coenzyme Q10 quantification in purple non-sulfur bacteria.

A recent focus has been on the recovery of single-cell protein and other nutritionally valuable bioproducts, such as Coenzyme Q10 (CoQ10) from purple non-sulfur bacteria (PNSB) biomass following wastewater treatment. However, due to PNSB's peculiar cell envelope (e.g., increased membrane cross-section for energy transduction) and relatively smaller cell size compared to well-studied microbial protein sources like yeast and microalgae, the effectiveness of common cell disruption methods for protein quantification from PNSB may differ. Thus, this study examines the efficiency of selected chemical (NaOH and EDTA), mechanical (homogenization and bead milling), physical (thermal and bath/probe sonication), and combined chemical-mechanical/physical treatment techniques on the PNSB cell lysis. PNSB biomass was recovered from the treatment of gas-to-liquid process water. Biomass protein and CoQ10 contents were quantified based on extraction efficiency. Considering single-treatment techniques, bead milling resulted in the best protein yields (p < 0.001), with the other techniques resulting in poor yields. However, the NaOH-assisted sonication (combined chemical/physical treatment technique) resulted in similar protein recovery (p = 1.00) with bead milling, with the former having a better amino acid profile. For example, close to 50% of the amino acids, such as sensitive ones like tryptophan, threonine, cystine, and methionine, were detected in higher concentrations in NaOH-assisted sonication (>10% relative difference) compared to bead-milling due to its less disruptive nature and improved solubility of amino acids in alkaline conditions. Overall, PNSB required more intensive protein extraction techniques than were reported to be effective on other single-cell organisms. NaOH was the preferred chemical for chemical-aided mechanical/physical extraction as EDTA was observed to interfere with the Lowry protein kit, resulting in significantly lower concentrations. However, EDTA was the preferred chemical agent for CoQ10 extraction and quantification. CoQ10 extraction efficiency was also suspected to be adversely influenced by pH and temperature.

Anti-Microbial Activities of Mussel-Derived Recombinant Proteins against Gram-Negative Bacteria.

Many anti-microbial peptides (AMPs) and pro-apoptotic peptides are considered as novel anti-microbial agents, distinguished by their different characteristics. Nevertheless, AMPs exhibit certain limitations, including poor stability and potential toxicity, which hinder their suitability for applications in pharmaceutics and medical devices. In this study, we used recombinant mussel adhesive protein (MAP) as a robust scaffold to overcome these limitations associated with AMPs. Mussel adhesive protein fused with functional peptides (MAP-FPs) was used to evaluate anti-microbial activities, minimal inhibitory concentration (MIC), and time-kill kinetics (TKK) assays against six of bacteria strains. MAP and MAP-FPs were proved to have an anti-microbial effect with MIC of 4 or 8 µM against only Gram-negative bacteria strains. All tested MAP-FPs killed four different Gram-negative bacteria strains within 180 min. Especially, MAP-FP-2 and -5 killed three Gram-negative bacteria strain, including E. coli, S. typhimurium, and K. pneumoniae, within 10 min. A cytotoxicity study using Vero and HEK293T cells indicated the safety of MAP and MAP-FP-2 and -3. Thermal stability of MAP-FP-2 was also validated by HPLC analysis at an accelerated condition for 4 weeks. This study identified that MAP-FPs have novel anti-microbial activity, inhibiting the growth and rapidly killing Gram-negative bacteria strains with high thermal stability and safety.

Enhanced Microbial Protein Production from CO2 and Air by a MoS2 Catalyzed Bioelectrochemical System.

Carbon dioxide can be relatively easily reduced to organic matter in a bioelectrochemical system (BES). However, due to insufficient reduction force from in-situ hydrogen evolution, it is difficult for nitrogen reduction. In this study, MoS2 was firstly used as an electrocatalyst for the simultaneous reduction of CO2 and N2 to produce microbial protein (MP) in a BES. Cell dry weight (CDW) could reach 0.81±0.04 g/L after 14 d operation at -0.7 V (vs. RHE), which was 108±3 % higher than that from non-catalyst control group (0.39±0.01 g/L). The produced protein had a better amino acid profile in the BES than that in a direct hydrogen system (DHS), particularly for proline (Pro). Besides, MoS2 promoted the growth of bacterial cell on an electrode and improved the biofilm extracellular electron transfer (EET) by microscopic observation and electrochemical characterization of MoS2 biocathode. The composition of the microbial community and the relative abundance of functional enzymes revealed that MoS2 as an electrocatalyst was beneficial for enriching Xanthobacter and enhancing CO2 and N2 reduction by electrical energy. These results demonstrated that an efficient strategy to improve MP production of BES is to use MoS2 as an electrocatalyst to shift amino acid profile and microbial community.

Effects of nitrogen supply on hydrogen-oxidizing bacterial enrichment to produce microbial protein: Comparing nitrogen fixation and ammonium assimilation.

To investigate the effects of nitrogen source supply on microbial protein (MP) production by hydrogen-oxidizing bacteria (HOB) under continuous feed gas provision, a sequencing batch culture comparison (N2 fixation versus ammonium assimilation) was performed. The results confirmed that even under basic cultivation conditions, N2-fixing HOB (NF-HOB) communities showed higher levels of CO2 and N2 fixation (190.45 mg/L Δ CODt and 11.75 mg/L Δ TNbiomass) than previously known, with the highest biomass yield being 0.153 g CDW/g COD-H2. Rich ammonium stimulated MP synthesis and the biomass accumulation of communities (increased by 7.4 ～ 14.3 times), presumably through the enhancement of H2 and CO2 absorption. The micro mechanism may involve encouraging the enrichment of species like Xanthobacter and Acinetobacter then raising the abundance of nitrogenase and glutamate synthase to facilitate the nitrogen assimilation. This would provide NF-HOB with ideas for optimizing their MP synthesis activity.

Estimating Microbial Protein Synthesis in the Rumen-Can 'Omics' Methods Provide New Insights into a Long-Standing Question?

Rumen microbial protein synthesis (MPS) provides at least half of the amino acids for the synthesis of milk and meat protein in ruminants. As such, it is fundamental to global food protein security. Estimating microbial protein is central to diet formulation, maximising nitrogen (N)-use efficiency and reducing N losses to the environment. Whilst factors influencing MPS are well established in vitro, techniques for in vivo estimates, including older techniques with cannulated animals and the more recent technique based on urinary purine derivative (UPD) excretion, are subject to large experimental errors. Consequently, models of MPS used in protein rationing are imprecise, resulting in wasted feed protein and unnecessary N losses to the environment. Newer 'omics' techniques are used to characterise microbial communities, their genes and resultant proteins and metabolites. An analysis of microbial communities and genes has recently been used successfully to model complex rumen-related traits, including feed conversion efficiency and methane emissions. Since microbial proteins are more directly related to microbial genes, we expect a strong relationship between rumen metataxonomics/metagenomics and MPS. The main aims of this review are to gauge the understanding of factors affecting MPS, including the use of the UPD technique, and explore whether omics-focused studies could improve the predictability of MPS, with a focus on beef cattle.

Dietary replacement of soybean meal with heat-treated grain soybean in diets of feedlot-finished beef cattle: impacts on intake, digestibility, and ruminal parameters.

The objective of this study was to assess the impact of increasing levels of heat-treated soybean in the diet of crossbred cattle during the finishing phase on nutrient intake and digestibility, ruminal parameters, digesta passage rate, nitrogen balance, and microbial protein synthesis. Five steers, crossbred 7/8 Jersey x Zebu, fitted with rumen cannulas and with an average weight of 350 ± 50 kg, were utilized. The experimental treatments consisted of 0, 7, 14, 21, and 28% inclusion of heat-treated soybean in the total diet dry matter. The animals were randomly allocated in a 5 × 5 Latin square design. Evaluation of the animals took place over five experimental periods, each lasting 20 days. During each experimental period, the first 15 days were allocated for animal adaptation to the experimental diets, followed by five days of data collection. No significant differences were observed among the diets in terms of dry matter intake (average of 6.57 kg day-1; P = 0.615) and organic matter intake (average of 6.23 kg day-1; P = 0.832). However, heat-treated soybean had a significant impact on the digestibility of dry matter (P = 0.02), organic matter (P = 0.01), crude protein (P < 0.01), and neutral detergent fiber (P < 0.01). There was no observed change on microbial protein synthesis (average of 409.6 g day-1) in animals with the inclusion of heat-treated soybean in the diets. With each 1% inclusion of heat-treated soybean in the cattle diet, there was an increase of 0.00754 units in ruminal pH values and a reduction of 0.75839 mg dL-1 in ruminal ammoniacal nitrogen values. This study suggests that heat-treated soybean can be included in up to 15% of the dry matter in diets for finishing feedlot cattle.

Estimation of microbial protein synthesis in the rumen of growing lambs based on the purine derivative excretions and the dietary forage-to-concentrate ratio.

Objective: Estimating microbial protein synthesis (MPS) in the rumen of growing lambs based on the urinary excretion of purine derivatives (PDs) and forage to concentrate (F/C) ratio. Materials and Methods: 36 similar-growing male lambs (weight 32.53 ± 1.90 kg; age 93 ± 6.63 days) were used in a completely randomized design with four groups: a) the 20-80 F/C ratio (dry hay 10% + wheat straw 10%), b) the 20-80 F/C ratio (dry hay 0% + wheat straw 20%), c) the 10-90 F/C ratio (dry hay 5% + wheat straw 5%), d) and the 10-90 F/C ratio (dry hay 0% + wheat straw 10%) with nine replicates. Results: Total PD and rumen MPS synthesized increased (10.98 vs. 13.25 mmol/day and 59.45 vs. 71.80 gm/day) in group d compared to group a. Dry organic matter intake (0.869 kg/day), fermentable dry organic matter (0.563 kg/day), and microbial nitrogen (N) yield (11.48 gm/day) of group d were at the maximum, but in terms of gN/kg dry organic matter (22.37 gm/kg), the mean of group c was higher than others. Conclusion: Increasing the level of food concentrate and the gradual removal of alfalfa from the diet increased the excretion of PD and MPS in the rumen. It was also found that urinary PD monitoring is an accurate indicator for the estimation of MPS.

Research updates and progress on nutritional significance of the amides I and II, alpha-helix and beta-sheet ratios, microbial protein synthesis, and steam pressure toasting condition with globar and synchrotron molecular microspectroscopic techniques with chemometrics.

This article aims to review research updates and progress on the nutritional significance of the amides I and II, the alpha-helix and beta-sheet ratios, the microbial protein synthesis, and the steam pressure toasting condition in food and feed with globar and synchrotron molecular microspectroscopic techniques plus chemometrics (both univariate and multivariate techniques). The review focused on (I) impact of the amides I and II, and the alpha-helix and beta-sheet-structure ratios in food and feeds; (II) Current research progress and update in synchrotron technique and application in feed and food molecular structure studies that are associated with nutrition delivery; (III) Impact of thermal processing- steam pressure toasting condition on feed and food; (IV). Impact of the microbial protein synthesis and methodology on feed and food; and (V). Impact on performance and production of ruminants with Faba beans.

Digestibility and nitrogen balance of goats on high and low protein rations supplemented with a commercial tannin feed-additive.

Despite the increasing importance of goat production in response to high demand for their products and their relative robustness to environmental stressors, and in contrast to other ruminant species, little data is available on how tannin extract feeding affects their feed intake, nutrient digestion and nitrogen (N) metabolism. Therefore, a trial in Oman investigated the respective variables by using a commercial tannin feed additive. In a 4 (treatments) x 3 (periods) x 2 (animals) Youden square, two weaned Batinah bucks each were fed a high or low protein diet of Rhodes grass hay and crushed barley grain, with or without the addition of a chestnut and quebracho tannin extract at 2 g/kg metabolic weight. Feed offered, feed refused and faeces and urine excreted were quantified to determine diet digestibility, total N excretion, N retention and rumen microbial protein synthesis (MPS). Due to their young age and low live weight, feed intake of goats was relatively low. Crude protein level and tannin addition had no statistically significant effect on dry matter (DM) and N intake, DM digestibility, N excretion in faeces and urine, as well as MPS. In consequence, no benefit of tannin feeding could be confirmed for the goats' N retention, irrespective of diet composition. These results indicate, on one hand, an effective neutralisation of the tested tannin extract along the gastrointestinal tract of goats, but on the other hand, that stimulation of MPS or N retention by tannins cannot be evidenced when diet components are present that simultaneously release energy and protein, as is the case with barley.

Anti bacterial function of secreted human FABP3.

FABP3 belongs to a large family of cytoplasmic fatty acid binding proteins that are expressed in a tissue-specific manner. It is predominantly expressed in breast, muscle and heart. During our exploratory studies on the role of FABP3 in tumorigenesis and our consequent attempts to study the molecular mechanism responsible for the oncogenic potential of FABP3, we came across an unexpected role of FABP3 as an anti-bacterial protein. Presence of the protein was detected in culture media of cell lines stably over-expressing human FABP3. Conditioned medium from these FABP3 over-expressing cells exerted a distinct anti-bacterial activity against E. coli. Our results indicate that binding of FABP3 to the bacterial cell surface contributes to its anti-bacterial activity. Incubation of E. coli bacterial cells with FABP3 protein led to disruption of the physical integrity of bacterial cell membrane causing leakage of cellular components. Further, in silico analysis predicted strong binding of FABP3 to the antibiotic binding sites on the bacterial ribosome. Interestingly, we found that FABP3 is a naturally occurring secretory protein present in milk in abundance as confirmed by western blot and ELISA. Thus, our experimental data together with in silico analysis suggests that FABP3 is secreted in milk, has an anti-bacterial function, shows activity against E. coli by disrupting bacterial membrane and targeting the ribosome, and may play a protective role against bacterial infection in newborns.

In-situ microbial protein production by using nitrogen extracted from multifunctional bio-electrochemical system.

Upgrading of waste nitrogen sources is considered as an important approach to promote sustainable development. In this study, a multifunctional bio-electrochemical system with three chambers was established, innovatively achieving 2.02 g/L in-situ microbial protein (MP) production via hydrogen-oxidizing bacteria (HOB) in the protein chamber (middle chamber), along with over 2.9 L CO2/(L·d) consumption rate. Also, 69% chemical oxygen demand was degraded by electrogenic bacteria in the anode chamber, resulting in the 394.67 J/L electricity generation. Focusing on the NH4+-N migration in the system, the current intensity contributed 4%-9% in the anode and protein chamber, whereas, the negative effect of -6.69% on contribution was shown in the cathode chamber. On the view of kinetics, NH4+-N migration in anode and cathode chambers was fitted well with Levenberg-Marquardt equation (R2 > 0.92), along with the well-matched results of HOB growth in the protein chamber based on Gompertz model (R2 > 0.99). Further evaluating MPs produced by HOB, 0.45 g/L essential amino acids was detected, showing the better amino acid profile than fish and soybean. Multifunctional bio-electrochemical system revealed the economic potential of producing 6.69 €/m3 wastewater according to a simplified economic evaluation.

Microbial protein production from lactose-rich effluents through food-grade mixed cultures: Effect of carbon to nitrogen ratio and dilution rate.

Overabundant agro-industrial side streams such as lactose-rich effluents from dairy activities offer multiple valorisation opportunities. In the present study, a food-grade mixed culture of bacteria and yeasts was tested under different operational conditions for the treatment and the valorisation of cheese whey permeate (CWP), the residue of whey protein recovery, into microbial protein (MP). Under continuous aerobic fermentation settings, the carbon-to-nitrogen (C/N) ratio showed little to no influence on the system performances and MP quality as compared to dilution rates (D), leading to a final protein content as high as 76%. Under high D values, instead, while biomass productivity increased, N-efficiency and protein content decreased. Unlike the bacterial community, the yeast one proved to be highly stable and less influenced by the increase of D. A preliminary estimate indicated that 2-11% of the future MP-based food production could be satisfied by only valorising lactose-rich dairy residues such as CWP.

Supplementing branched-chain volatile fatty acids in dual-flow cultures varying in dietary forage and corn oil concentrations. I: Digestibility, microbial protein, and prokaryotic community structure.

Branched-chain amino acids are deaminated by amylolytic bacteria to branched-chain volatile fatty acids (BCVFA), which are growth factors for cellulolytic bacteria. Our objective was to determine the dietary conditions that would increase the uptake of BCVFA by rumen bacteria. We hypothesized that increased forage would increase cellulolytic bacterial abundance and incorporation of BCVFA into their structure. Supplemental polyunsaturated fatty acids, supplied via corn oil (CO), should inhibit cellulolytic bacteria growth, but we hypothesized that additional BCVFA would alleviate that inhibition. Further, supplemental BCVFA should increase neutral detergent fiber degradation and efficiency of bacterial protein synthesis more with the high forage and low polyunsaturated fatty acid dietary combination. The study was an incomplete block design with 8 dual-flow continuous cultures used in 4 periods with 8 treatments (n = 4 per treatment) arranged as a 2 × 2 × 2 factorial. The factors were: high forage (HF) or low forage (LF; 67 or 33%), without or with supplemental CO (3% dry matter), and without or with 2.15 mmol/d (which included 5 mg/d of 13C each of BCVFA isovalerate, isobutyrate, and 2-methylbutyrate). The isonitrogenous diets consisted of 33:67 alfalfa:orchardgrass pellet, and was replaced with a concentrate pellet that mainly consisted of ground corn, soybean meal, and soybean hulls for the LF diet. The main effect of supplementing BCVFA increased neutral detergent fiber (NDF) degradability by 7.6%, and CO increased NDF degradability only in LF diets. Supplemental BCVFA increased bacterial N by 1.5 g/kg organic matter truly degraded (6.6%) and 0.05 g/g truly degraded N (6.5%). The relative sequence abundance decreased with LF for Fibrobacter succinogenes, Ruminococcus flavefaciens, and genus Butyrivibrio compared with HF. Recovery of the total 13C dose in bacterial pellets decreased from 144 µg/ mg with HF to 98.9 µg/ mg with LF. Although isotope recovery in bacteria was greater with HF, BCVFA supplementation increased NDF degradability and efficiency of microbial protein synthesis under all dietary conditions. Therefore, supplemental BCVFA has potential to improve feed efficiency in dairy cows even with dietary conditions that might otherwise inhibit cellulolytic bacteria.

Comparing the standardized amino acid digestibility of an alternative protein source with commercially available protein-based ingredients using the precision-fed cecectomized rooster assay.

Using single-cell-based proteins in pet foods is of interest, but little testing has been done. Therefore, our objective was to determine the amino acid (AA) digestibilities, assess protein quality of a novel microbial protein (MP) (FeedKind), and compare it with other protein-based ingredients using the precision-fed cecectomized rooster assay. Test ingredients included: MP, chicken meal (CM), corn gluten meal (CGM), pea protein (PP), and black soldier fly larvae. Thirty cecectomized roosters (n = 6/ingredient) were randomly assigned to test ingredients. After 24 h of feed withdrawal, roosters were tube-fed 15 g test ingredient and 15 g corn, and then excreta were collected for 48 h. Endogenous AA corrections were made using additional roosters. Digestible indispensable AA score (DIAAS)-like values were calculated to determine protein quality according to Association of American Feed Control Officials (AAFCO), The European Pet Food Industry Federation, and National Research Council reference values for growing and adult dogs and cats. Data were analyzed using the Mixed Models procedure of SAS 9.4, with P ≤ 0.05 being significant. All reactive lysine:total lysine ratios, an indicator of heat damage, were higher than 0.9, except for CM (0.86). Digestibility of indispensable and dispensable AA were >85% and >80% for MP, respectively, with indispensable AA digestibilities being >80% for all other ingredients. In general, CGM had the highest, while CM had the lowest AA digestibilities. Two exceptions were lysine and tryptophan. Lysine digestibility for MP was higher than that of all other ingredients, while tryptophan digestibility for MP was higher than that of CM, CGM, and PP. Threonine digestibility was highest for CGM and MP. Valine digestibility was highest for CGM, PP, and MP. DIAAS-like calculations identified limiting AA of each ingredient and depended on the reference used and life stage and species of animal. Using AAFCO guidelines, all DIAAS-like values for MP were >100 suggesting that it could be used as the sole source of protein in adult dog and cat diets; only methionine had DIAAS-like values <100 for growing kittens. For dogs, limiting AA was most commonly methionine, threonine, and tryptophan in the other protein sources. For cats, limiting AA was most commonly lysine and methionine. Lysine was severely limited in CGM across all life stages considered. Further research in dogs and cats is necessary, but our data suggest that the MP tested has high AA digestibilities and is a high-quality protein source that may be useful in pet foods.

Single-cell-based proteins are of interest for use in pet foods, but little testing has been done. The objective of this experiment was to compare the amino acid (AA) digestibilities and protein quality of a novel microbial protein (MP) (FeedKind) with chicken meal (CM), corn gluten meal (CGM), pea protein (PP), and black soldier fly larvae ingredients using the precision-fed cecectomized rooster assay. Cecectomized roosters were tube-fed the test ingredients and excreta were collected. All reactive lysine:total lysine ratios, an indicator of heat damage, were higher than 0.9, except for CM. Digestibility of indispensable and dispensable AA were >85% and >80% for MP, respectively, with indispensable AA digestibilities being >80% for all other ingredients. In general, CGM had the highest, while CM had the lowest AA digestibilities. Lysine and tryptophan were exceptions, being highest for MP. Threonine and valine digestibilities were also high for MP. Digestible indispensable AA score-like values identified limiting AA of each ingredient. Limiting AA was most commonly methionine, threonine, and tryptophan for dogs and lysine and methionine for cats. Our data suggest that the MP tested has high AA digestibilities and is a high-quality protein source that may be useful in pet foods.

From anaerobic digestion to single cell protein synthesis: A promising route beyond biogas utilization.

The accumulation of a large amount of organic solid waste and the lack of sufficient protein supply worldwide are two major challenges caused by rapid population growth. Anaerobic digestion is the main force of organic waste treatment, and the high-value utilization of its products (biogas and digestate) has been widely concerned. These products can be used as nutrients and energy sources for microorganisms such as microalgae, yeast, methane-oxidizing bacteria(MOB), and hydrogen-oxidizing bacteria(HOB) to produce single cell protein(SCP), which contributes to the achievement of sustainable development goals. This new model of energy conversion can construct a bioeconomic cycle from waste to nutritional products, which treats waste without additional carbon emissions and can harvest high-value biomass. Techno-economic analysis shows that the SCP from biogas and digestate has higher profit than biogas electricity generation, and its production cost is lower than the SCP using special raw materials as the substrate. In this review, the case of SCP-rich microorganisms using anaerobic digestion products for growth was investigated. Some of the challenges faced by the process and the latest developments were analyzed, and their potential economic and environmental value was verified.