Growth and biochemical characterization of green and red strains of the tropical agarophytes Gracilaria debilis and Gracilaria edulis (Gracilariaceae, Rhodophyta)

Abstract

Cultivation of the wild-type red strain and green natural mutant strains of Gracilaria debilis (Forsskal) Borgesen (RD and GD) and Gracilaria edulis (Gmelin) Silva (RE and GE) was attempted by raft method from August, 2014 to May, 2015 at Thonithurai, southeastern coast of India, for 180 days in order to evaluate color stability, growth rates, pigment composition, sap components, and the agar yield and quality. Coloration pattern of green and red strains of G. debilis and G. edulis was fixed, and no interchange in color occurred during the cultivation. Red strains of both G. edulis (RE) and G. debilis (RD) showed higher performance in biomass yield and phycoerythrin content over their green counterparts. Maximum biomass yields of 12.458 ± 1.24 kg fresh wt m−2 and 5.49 ± 0.26 kg fresh wt m−2 were observed in G. debilis and G. edulis, respectively. Higher DGR of 5.82 ± 0.57 % day−1 and 5.42 ± 1.73 % day−1 were observed in G. edulis and G. debilis, respectively. Highest gel strength recorded in G. debilis was 800 ± 15 g cm−2 and followed by G. edulis 695 ± 15 g cm−2. Green and red strain of G. debilis (GD and RD) and G. edulis (GE and RE) showed similar pattern in DGR, phycocyanin and allophycocyanin content, agar yield, gel strength, gelling temperature, melting temperature, sulfate content, and mineral composition of sap (p > 0.05). The growth rates observed in green and red strains of both species were considered adequate for commercial farming, and the present agar-related data fulfilled the industrial and pharmaceutical requirements.