Nitrogen fixation associated with sago (Metroxylon sagu) and some implications

Abstract

Aims:  To determine the presence and contribution of diazotrophic bacteria to nitrogen concentrations in edible starch derived from the sago palm (Metroxylon sagu).

Methods and Results:  Isolation of diazotrophic bacteria and analysis of nitrogen fixation were conducted on pith, root and sago starch samples. Acetylene reduction showed that five of ten starch samples were fixing nitrogen. Two presumptive nitrogen-fixing bacteria from starch fixed nitrogen in pure culture and five isolates were positive for the nif H gene. Nitrogen concentrations in 51 starch samples were low (37 samples <0·2 g kg−1; 14 ranging from 0·2 to 2·0 g kg−1).

Conclusions:  Nitrogen fixation occurs in sago starch, which undoubtedly plays a role in fermentation ecology. Nitrogen levels are considered too low to be of nutritional benefit and to protect against nutritional-associated illnesses.

Significance and Impact of the Study:  Sago starch does not add significantly to the protein calorie intake and may be associated with susceptibility to nutritional-associated illness.