Bioprocess Engineering Aspects of Biopolymer Production by the CyanobacteriumSpirulinaStrain LEB 18

Microbial biopolymers can replace environmentally damaging plastics derived from petrochemicals. We investigated biopolymer synthesis by the cyanobacterium Spirulina strain LEB 18. Autotrophic culture used unmodified Zarrouk medium or modified Zarrouk medium in which the NaNO 3 content was reduced to 0.25 g L −1 and the NaHCO 3 content reduced to 8.4 g L −1 or increased to 25.2 g L −1 . Heterotrophic culture used modified Zarrouk medium containing 0.25 g L −1 NaNO 3 with the NaHCO 3 replaced by 0.2 g L −1 , 0.4 g L −1 , or 0.6 g L −1 of glucose (C 6 H 12 O 6 ) or sodium acetate (CH 3 COONa). Mixotrophic culture used modified Zarrouk medium containing 0.25 g L −1 NaNO 3 plus 16.8 g L −1 NaHCO 3 with the addition of 0.2 g L −1 , 0.4 g L −1 , or 0.6 g L −1 of glucose or sodium acetate. The highest biopolymer yield was 44% when LEB 18 was growing autotrophically in media containing 0.25 g L −1 NaNO 3 and 8.4 g L −1 NaHCO 3 .