Effects of Hydrolysis pH on Distribution of Molecular Weights of Alginates of Sea Tangle Laminaria japonica

To prepare oligouronic acids from high-molecular-weight alginates, sea tangle (Laminaria japonica) alginates were hydrolyzed at various pHs for 1 hr at 80$^{\circ}C$. The effects of hydrolysis pH (HpH) on the average molecular weight (AMW) and MW distribution ratios (DRs) in the hydrolyzed alginates were investigated. As HpH decreased, the DRs of the alginates with MW>500 kDa and MW=300-500 kDa decreased exponentially, while it increased exponentially for MW<50 kDa. For MW=100-300 kDa, DR increased exponentially as HpH fell from 5.0 to 3.5, and then decreased exponentially. Similarly, for MW=50-100 kDa, DR increased exponentially as HpH increased to 1.0 from 5.0, and then decreased exponentially. As HpH decreased, the MW cutoff size and AMW of alginates fraction with the highest DR were decreased. For HpH 4.5 and 5.0, the MW cutoff size with the highest DRs was MW=300-500 kDa; the DRs were 28.9 and 32.6%, respectively; and the AMW of both was about 400 kDa, for HpH 3.5 and 4.0, the cutoff size was MW=100-300 kDa; the DRs were about 28%: and the AMWs were both about 200 kDa. For HpH 3.0, the cutoff size was MW=50-100; the DR was 29.0%; and the AMW was 73 kDa. For HpH values below 2.0, the MW cutoff size with the highest DRs was MW<50 kDa, and all of the AMWs were below 28 kDa.

다시마 (Laminaria japonica) 알긴산의 분자량 분포에 미치는 가수분해 pH의 영향