title: Improvement of ε-poly-L-lysine production through seed stage development based on in situ pH monitoring.
abstract: Nissin, natamycin, and ε-poly-L-lysine (ε-PL) are three safe, microbial-produced food preservatives used today in the food industry. However, current industrial production of ε-PL is only performed in several countries. In order to realize large-scale ε-PL production by fermentation, the effects of seed stage on cell growth and ε-PL production were investigated by monitoring of pH in situ in a 5-L laboratory-scale fermenter. A significant increase in ε-PL production in fed-batch fermentation by Streptomyces sp. M-Z18 was achieved, at 48.9 g/L, through the optimization of several factors associated with seed stage, including spore pretreatment, inoculum age, and inoculum level. Compared with conventional fermentation approaches using 24-h-old shake-flask seed broth as inoculum, the maximum ε-PL concentration and productivity were enhanced by 32.3 and 36.6 %, respectively. The effect of optimized inoculum conditions on ε-PL production on a large scale was evaluated using a 50-L pilot-scale fermenter, attaining a maximum ε-PL production of 36.22 g/L in fed-batch fermentation, constituting the first report of ε-PL production at pilot scale. These results will be helpful for efficient ε-PL production by Streptomyces at pilot and plant scales.
authors.affiliation: The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, People's Republic of China.
authors.forename: Qi-Xing
authors.initials: QX
authors.lastname: Sun
authors.forename: Xu-Sheng
authors.initials: XS
authors.lastname: Chen
authors.forename: Xi-Dong
authors.initials: XD
authors.lastname: Ren
authors.forename: Zhong-Gui
authors.initials: ZG
authors.lastname: Mao
mesh_terms: D061249:Batch Cell Culture Techniques / Q000295:instrumentation / Q000379:methods; D019149:Bioreactors; D005285:Fermentation; D005520:Food Preservatives / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D011107:Polylysine / Q000096:biosynthesis*; D013171:Spores, Bacterial / Q000378:metabolism*; D013302:Streptomyces / Q000378:metabolism*
chemical_list: D005520:Food Preservatives; D011107:Polylysine; D005947:Glucose; D005990:Glycerol