Premium
Effects of intermittent addition of cellulase for production of L ‐lactic acid from wastewater sludge by simultaneous saccharification and fermentation
Author(s) -
Nakasaki Kiyohiko,
Adachi Tomohiko
Publication year - 2003
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.10573
Subject(s) - lactic acid , cellulase , fermentation , hydrolysis , chemistry , food science , cellulose , bacteria , wastewater , biochemistry , pulp and paper industry , biology , waste management , genetics , engineering
An attempt was made to create L ‐lactic acid, a precursor of poly‐lactic acid, which is a biodegradable plastic, from wastewater sludge from the paper‐manufacturing industry. The sludge contained a high percentage of cellulose and needed to be hydrolyzed to glucose by the action of the cellulase before being treating with lactic acid bacteria. Therefore, a method involving simultaneous saccharification and fermentation (SSF) was carried out. The optimum pH of the SSF for production of the lactic acid by the newly isolated lactic acid bacterium with a high selectively of L ‐lactic acid was found out to be around pH = 5.0, and the optimum temperature to be approximately 40°C. On the basis of the measurement of the cell density changes in the lactic acid bacteria, it was ascertained that the bacterial activity could continue at a high level for a relatively long period of time, and that the L ‐lactic acid productivity was diminished by the rapid deactivation of the cellulase. With the intermittent addition of cellulase once daily for the sake of compensating for the cellulase deactivation, the L ‐lactic acid attained a maximum concentration of 16.9 g/L, i.e., a 72.2% yield based on the potential glucose contained in the sludge under optimum pH and temperature conditions.© 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 263–270, 2003.