Chemical Quality and Production of Agars Extracted from Gracilaria tikvahiae Grown in Different Nitrogen Enrichment Conditions

Increasing concentrations of nitrogen fertilizer led to increased growth and internal nitrogen content of Gracilaria tikvahiae and decreased yields of agar. The thallus nitrogen content was highly correlated with percent protein and protein:carbohydrate ratios, and percent agar was highly correlated with percent carbohydrate. Agars extracted from thalli grown under nitrogen enriched conditions had higher melting temperatures and greater gel strengths than did agars extracted from less enriched thalli. The data suggest that the increased gel strengths found in these experiments may be due to the greater molecular size of the agar polymers, as indicated by the increased melting temperatures associated with greater gel strengths.