Table 4.

Recent studies using anoxygenic phototrophic bacteria for single-cell protein production and resource recovery.

ORGANISM	CULTURE ORIGIN	TARGET	CULTURE CONDITIONS	PROTEIN CONTENT	ADDITIONAL OUTCOME	REFERENCE
Rhodopseudomonas faecalis PA2	Wastewater treatment pond	Animal feed additive	Anoxygenic growth in photobioreactor. 2000−4000 lux. Optimal growth was at light intensity of 4000 lx at 150 rpm	64.8 % protein. Essential amino acids (required for penaeid shrimp) accounted for 72.6 % of total protein content.	Carotenoid and bacteriochlorophyll produced	[191]
Rhodopseudomonas	Local pond	SCP	Dark aerobic conditions on biogas slurry with a salinity of 1.38 %	Protein content could be enhanced up to 90 % due to high ammonia and salinity of the biogas slurry	Upregulation of glutamate synthase and glutamine synthetase activity, that indicated enhanced glutamine and glutamate biosynthesis	[192]
Rhodobacter sphaeroides SS15, S3 W10, TKW17 and Afifella marina STW181	Isolated from shrimp ponds in south Thailand	Source of protein for Litopenaeus vannamei (white shrimp)	Cultured under basic isolation media with 1.5 % NaCl (R. sphaeroides) and glutamate acetate medium with 2% NaCl (A. marina) under photo-microaerobic conditions	Protein content for R. sphaeroides SS15 was the highest at 53.98 ± 0.08%, whereas for A. marina STW181 it was 49.06 ± 0.10 and the essential amino acid profile of these strains were higher than the essential amino acid requirements for shrimp	Among the different diet formulations tested, Diet 1 comprising of 1% commercial shrimp feed mixed with 0.5 % each of R. sphaeroides SS15 and A. marina STW181, was the most effective shrimp feed and it enhanced shrimp growth and survival.	[193]
Rhodopseudomonas	Local pond	Resource recovery	Artificial brewery wastewater cultivated in photobioreactors with natural light and microaerobic conditions	420.9 mg/g	The bacteria were rich in polysaccharides, carotenoids, bacteriochlorophyll and coenzyme Q10 (antioxidant)	[194]
Mixed purple phototrophic bacteria (PPB) inoculum	Enriched from wastewater	Fish meal replacement for Lates calcarifer (Asian sea bass)	Photo anaerobic bioreactor with Ormerod medium	> 57 %	Up to 66 % of fishmeal could be replaced with purple phototrophic bacteria and this did not cause any adverse effect on fish. Total amino acid present was highest when PPB replaced 66% and 100% of fishmeal.	[195]
PPB cultures initially dominated by Allochromatium sp. and Rhodobacter sp. but eventually by Rhodovulum sp.	Brisbane river water and mud sediments	Treatment of highly saline wastewater	Raw domestic wastewater was used as a substrate. Cultivation was carried out in a continuous infra-red photo anaerobic membrane reactor	0.62(0.21) gCP/gVS crude protein.	COD:N:P removal was 100:6:5:1.0 with 0.8 g COD/ gCODfed	[196]
Rhodopseudomonas faecalis PA2	–	Animal feed	Cultures were initially grown on a glutamate malate medium in anaerobic light conditions. Wastewater from the sugar industry in Thailand was used for cultivation of the bacteria under microaerobic conditions	>50 %. All essential amino acids were present. Methionine, usually the limiting amino acid, was at higher concentrations than many other SCP sources.	Carotenoids production and COD reduction by 80 %	[197]