5.1 Conclusion
This thesis was performed to examine the probability of being an ideal alternative substrate for Monascus pigmentation of corn cob among agro-industrial residues tested as well as to determine the effects of moisture content and sugar supplementation on angkak pigment production by Monascus ruber. In addition, an attempt on de-polymerization of corn cob substrate by sulfuric acid and its effect on pigmentation were also investigated. The results showed that corn cob was the most appropriate substrate for Monascus compared to longan seed and sugarcane bagasse. 50% (w/w) moisture content was the most favorable condition for Monascus growth and thereby the angkak pigment yield, whereas the pigmentation suffered a drastic decline at substrate moisture content below 40% and above 70%. Addition of sugar as a carbon source exhibited positive influence on pigment production which particularly increased with increasing glucose concentration and topped out at 4% sugar added. Besides that, employing sulfuric acid in the de-polymerization of corn cob substrate gave a promising result of increased sugar content; however, this might not be favor the pigment yield due to the undesirable formation of degradation products and their inhibitory effects on fermenting organism.
5.2 Recommendation
Further researches need to be carried out in order to obtain an overall picture of how to optimize the de-polymerization of corn cob substrate as well as its effect on angkak pigmentation without inhibitors existence. First, the use of organic acids, such as maleic acid and fumaric acid accompanied with high temperature (160-220oC) and short residence time (a few minutes) may well reduce the formation of inhibitors while still keep the potential monomeric sugar yield for microbial fermentation. On the other hand, the first idea of using sulfuric acid to treat the corn cob substrate can be kept on condition that it is followed by a washing step to remove chemical residues prior to Monascus inoculation and enzyme is then introduced to continue the hydrolysis of the substrate during 3 weeks of incubation. Finally, an investigation of both investment cost and operational cost can also be necessary for commercial application in the future.