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The present study was conducted to evaluate the protein quality of microalgae species Chlorella vulgaris (CV), Chlorella sorokiniana (CS), and Acutodesmus obliquus (AO) and assess the impact of mechanical cell wall disruption. Male Sprague–Dawley rats, around 156 g after adaptation, were placed in metabolic cages and fed experimental diets that were either protein-free or contained 10% protein solely from one of the undisrupted or disrupted CV, CS, and AO. After 3 days, feces were collected for a period of 5 days and analyzed together with diet samples for crude protein contents. Apparent protein digestibility, true protein digestibility, amino acid score, and protein digestibility-corrected amino acid score were calculated. In vitro protein digestibility was measured using the pepsin–pancreatin method and the in vitro protein digestibility-corrected amino acid score was calculated. The crude protein contents of CV, CS, and AO were 53.5, 50.2, and 40.3%, respectively. The amino acid score of the first limiting amino acid was 1.10, 1.27, and 0.86, true protein digestibility was 64.7, 59.3, and 37.9% and protein digestibility-corrected amino acid score was 0.63, 0.64, and 0.29, respectively, for CV, CS, and AO. Mechanical cell disruption significantly improved protein digestibility without a substantial impact on the amino acid profile and score, resulting in the increase of protein digestibility-corrected amino acid score to 0.77, 0.81, and 0.46, respectively, for disrupted CV, CS, and AO. There was a strong correlation between in vitro protein digestibility and apparent protein digestibility (r = 0.986), and also between in vitro protein digestibility-corrected amino acid score and in vivo protein digestibility-corrected amino acid score (r = 0.994). The results suggest that the CV and CS are acceptable sources of protein for humans and animals and quality can be markedly improved by mechanical cell wall disruption. Additionally, in vitro protein digestibility measured using the pepsin–pancreatin method may be used to screen protein product candidates, save animals, reduce cost, and accelerate product development.

The objectives of the research were to compare the efficacy of ProVale yeast beta-glucan (b-glucan) with that of a previously tested research-grade yeast b-glucan preparation when administered as an intraperitoneal (IP) injection and to also pilot test the effectiveness of ProVale yeast b-glucan as a feed additive for reducing Loma salmonae xenoma formation on the gills of rainbow trout Oncorhynchus mykiss. Rainbow trout received IP injections of ProVale (4, 10, or 20 mg of ProVale/kg of fish) or Sigma b-glucan (4 mg/kg). Oral challenge with L. salmonae occurred 1 week after IP injection with the b-glucan products. For the second objective, 400 rainbow trout were separated into tanks and duplicate groups were treated with 0, 50, 100, and 200 g of ProVale/1,000 kg of feed. Starting at 3 weeks prior to challenge and continuing 2 weeks after challenge, rainbow trout were fed the various ProVale doses daily at a feeding rate of 1% of the fish biomass. Commencing at 4 weeks postchallenge, the fish in each trial were evaluated for the presence of xenomas on the first left gill arch. The most protective IP dose of commercial ProVale was 10 mg/kg when compared with the laboratorygrade IP dose of Sigma b-glucan (4 mg/kg). Both of these intraperitoneally administered b-glucan products were effective in reducing the mean xenoma count. ProVale used as a feed coating (200 g/1,000 kg) was able to reduce the mean xenoma count by 50%.

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BACKGROUND: Microalgae cultivation in wastewaters is a potential remediation technology for converting residual nutrients into valuable biomass for biofuels, fertilizers, animal and aquaculture feeds, and bio-based chemicals. The objective of this study was to determine the potential for microalgae phycoremediation of aquaculture and agriculture wastewaters for sustainable production of nutrient-rich algal biomass.RESULTS: Thirty-seven aquaculture and agriculture wastewaters were evaluated as growth media for two freshwater, chlorophytic microalgae strains (Chlorella sorokiniana SMC14M and Scenedesmus sp. AMDD). Although nutrient levels and physicochemical parameters of the wastewaters varied widely, phycoremediation efficiency of nitrogen and phosphorous was high (> 70%) for a large majority of them, with both microalgae strains. Photobioreactor cultivation (300 L) of C. sorokiniana grown on finfish aquaculture wastewater (CA2) and standard growth medium (SGM) exhibited similar biomass production levels and nutritional compositions of moisture (4.9-5.0%), ash (5.9-6.1%), nitrogen (8.6-8.8%), protein (41.0-42.1%), lipid (8.6-8.8%), carbohydrate (38.3-39.3%) and gross energy (22.2-22.3 MJÁkg −1 ) with highly similar fatty acid and amino acid profiles.CONCLUSIONS: This study demonstrates that the use of freshwater microalgae to remediate various aquaculture and agriculture wastewaters, while producing valuable nutrient-rich biomass, is feasible. We have found that a particular finfish aquaculture wastewater (CA2) contains all of the nutrients required for rapid microalgae growth, avoiding the need for expensive commercial fertilizers. The biochemical composition of C. sorokiniana grown on CA2 aquaculture wastewater has good potential for use as a nutrient-rich ingredient for animal and aquaculture feeds, fertilizers products, biofuels and other applications, resulting in remediated water that could be reused.