Integration of galacturonic acid extraction with alkaline protein extraction from green tea leaf residue

Leaf pectin can be used as a feedstock for galacturonic acid (GA) production, but high extraction costs limit economic feasibility. To improve the extraction efficiency, leaf pectin extraction was integrated with an already cost-effective alkaline protein extraction, focusing on high yield of GA without losses of protein. GA extraction efficiencies in NaOH, HCl, phosphate buffer solution, or with Viscozyme^® L were determined using green tea residues (GTR) as model material. Most GA was extracted using Viscozyme^® L, mainly due to its cellulase activity. Extraction yielded more than 95% GA with only 5% protein. Alternatively, GA-containing pectin can be extracted in a weak alkaline solution. Here, GA yield is dominated by the ratio of extraction volume to biomass weight. The profits of these two integrated processes can be higher than one step protein extraction. The Viscozyme^® L integrated process is suitable for GA production for application in chemicals, and may have a profit of 142$/ton GTR when enzyme cost are sufficiently lowered. The profit of the weak alkaline integrated process is estimated at 118$/ton GTR.