Abstract:
The main aim of this research project was to improve the efficiency of cassava starch enzymatically using the stirred tank lysis reactors which were firstly designed, developed and then scaled-up from the original one of 10-L to a 200-L pilot scale and finally 3,500-L industrial scale working with a private cassava company “Chor-ChaiWat” in Chon Buri province. The first two scales were used to study as research in details in the research chapters II, VII and VIII. In the meantime and at the beginning of this project, optimum conditions and kinetics of enzymatic hydrolysis of cassava starch from flour and root chip powder was studied in order to quantify the proper amounts of enzymes and starch and to find the optimum conditions (chapter I) for its hydrolysis for further studies at the large-scale. From the test tube work, then an in house 10-L lysis reactor was designed and fabricated by our group for the study of enzymatic hydrolysis of cassava starch in a stirred tank lysis reactor (chapter II). Very good results were obtained. We knew from our experiments and from literature review that, starch liquefaction and saccharification took very long process times of over three and twenty-four hours, respectively. To solve this problem, a new type state-of-the art in line static mixer reactor was specially designed and fabricated for starch liquefaction (chapter III). Essentially, it worked very well and liquefaction was done within only hour. From this success, confidently sugar dextrin saccharification also must be done using this procedure. Results showed that saccharification was completely done also within one hour (chapter IV). Surprisingly, more than twenty-hour faster reaction time when compare to using stirred tank reactor. The combination of research of chapter III and IV to generate the two-stage sequential continuous enzymatic hydrolysis of cassava starch through in-line static mixer reactor (chapter VI). Both liquefaction and saccharification process steps could be undertaken continuously with a residence reaction time of ~2 hours. Reducing sugar product of the DE value more than 98 was obtained. This was the great idea of creating the patent “two-stage sequential continuous enzymatic hydrolysis o cassava starch and/or continuous ethanol fermentation”. Using this in-line static mixer reactor, starch could be hydrolysed in one step by a strong acid (chapter V) instead of using two enzymes, alpha-amylase and glucoamylase for liquefaction and saccharification. This also gave a very good result and could be and alternative method for starch hydrolysis. Come back to a very good result of enzymatic hydrolysis of cassava starch in the 10-L stirred tank reactor. A 200-L stirred tank lysis reactor was designed and fabricated under the scale-up programme mentioned above and it was used to hydrolysed cassava starch (chapter VII). It also worked very well and could be used for being a prototype for an industrial scale reactor. In all research chapter, viscosity of starch products was studied because it was an important factor for process operation. Also, fast heat and mass transfer in the process of starch hydrolysis was studied using the cylinder of a rheometer as the reactor (chapter VIII). This research gave useful additional result. The result of these research works were interested by an industry “Chor-Chaiwat Co Ltd.” Nachom Tien, Chon Buri Province. Parts of technology from these research works have been transferred to that company and this co-operation has led the company being built a 3.5-tone stirred tank lysis reactor with a cost of 800,000 baht for hydrolysis of cassava starch (chapter IX).