Biochemical characterization of microalgal biomass from freshwater species isolated in Alberta, Canada for animal feed applications

Biochemical composition of freshwater microalgae isolates from Alberta, Canada was determined. Growth rate (0.98 ± 0.07 d− 1), biomass production (0.35 ± 0.03 g DW L− 1) and daily productivity (0.14 ± 0.01 g DW L− 1 d− 1) were the same for Chlorella vulgaris (AB02-C-U-BBM), Nannochloris bacillaris (AB03-C-F-PLM), Tetracystis sp. (AB04-C-F-PLM02) and Micractinium reisseri (AB05-C-U-BBM02). Whole algal biomass (WAB) contained low ash (~ 2 g 100 g DW− 1) and protein (13-15 g 100 g DW− 1), high esterifiable lipid (32-36 g 100 g DW− 1), carbohydrate (27-30 g 100 g DW− 1) and energy (26-28 MJ kg DW− 1). Oil fractionation was relatively ineffective for C. vulgaris and M. reisseri while oil was effectively extracted from N. bacillaris and Tetracystis sp. Accordingly, lipid-extracted biomass (LEB) from N. bacillaris and Tetracystis sp. contained higher protein (22 g 100 g DW− 1) and carbohydrate (43-44 g 100 g DW− 1) and lower residual esterifiable lipid (6-9 g 100 g DW− 1) than C. vulgaris and M. reisseri at 17-18 g 100 g DW− 1 (protein), 34-36 g 100 g− 1 DW (carbohydrate) and 28-32 g 100 g DW− 1 (residual esterifiable lipid). Biomass had favorable essential amino acid (EAA) profiles with high EAA indices (0.9-1.1); rich in first-limiting EAA lysine (0.9-1.5 g 100 g DW− 1). Fatty acids (% of total) were predominantly monounsaturated fatty acids (MUFA; 40-53%), high in polyunsaturated fatty acids (PUFA; 27-40%) and low in saturated fatty acids (14-24%). N. bacillaris and Tetracystis sp. were particularly rich (9-12%) in α-linolenic acid (18:3n − 3), had attractive n − 3:n − 6 ratios (0.5-0.7:1), were rich in iron (800-1616 mg kg DW− 1), had attractively low Ca:P ratios (0.6-0.9:1) and were virtually absent of contaminating heavy metals.