Nipa sap fermentation without yeast addition

Abstract

Bioethanol production from nipa sap was studied in this work. Nipa sap is a source of sugars, minerals, yeasts and nutrients which can be suitably used as a raw material for ethanol fermemtation. The nipa sap fermentation was carried out sufficiently using the native yeast in the sap without external yeast addition and nutrient supplementation. Firstly, the sap was pretreated with pH 4.9 at 36 ºC for 25 min before fermentation. Response Surface Methodology (RSM) was employed to design minimally experimental conditions of the fermentation and to optimize the conditions. The studied variables were initial total sugar concentration (10–30 %w/w), initial pH (4.5–6.5), temperature (28–40 ºC) and time (10–144 hours). The optimal condition using 22.4%w/w initial total sugar with pH 4.5 at 29ºC for 77 h could achieve 91% ethanol yield with 112.1 g/L ethanol concentration.