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In this work, sequential optimization strategy, based on statistical designs, was employed to enhance the generation of electricity in microbial fuel cell. For screening of growth medium composition significantly influencing electricity generation, the two-level Plackett–Burman design was used. Under our experimental conditions, glucose, KCl, and NaHCO3 were found to be the major factors of the electricity generation. A near optimum medium formulation was obtained using this method with increased voltage yield by 5.3 %. Response surface methodology was adopted to acquire the best process conditions. In this respect, the three-level Box–Behnken design was applied. A polynomial model was created to correlate the relationship between the three variables (glucose, KCl, and NaHCO3) and voltage yield. Estimated optimum levels of optimized variables for the generation of electricity were glucose 8.5 g/l, KCl 0.8 g/l, and NaHCO3 0.2 g/l. The optimum voltage yield was 738.72 mV which was 8.0 % than the basal medium.

Thirty bacterial isolates were obtained from different sources and sites at Jeddah, Saudi Arabia, on chitin agar medium; 9 of the 30 isolates were cultured in liquid medium containing chitin as sole carbon and nitrogen sources. Isolate SM21, which was isolated from shrimp shells, showed the best growth and chitinase production in liquid medium. According to its morphological, physiological and biochemical characteristics, SM21 belongs to the genus Streptomyces and was identified as Streptomyces anulatus SM21. Identification was confirmed using 16S rDNA analysis. The chitinase enzyme was precipitated with 80% NH4SO4 and purified using DEAE-cellulose ion exchange chromatography followed by Sephadex G-100 gel filtration. The molecular weight determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis was 28 kDa. Genetic improvement using the protoplast fusion technique was carried out between the identified Streptomyces isolate and Streptomyces coelicolor SM1. These two species, which have different resistance profiles to streptomycin and tetracycline (400 μg/ml and 10 μg/ml, respectively), were used in an intraspecific protoplast fusion using PEG 6000. The percentage of real protoplasts that could regenerate successfully was 71% for S. coelicolor SM1 and 80% for S. anulatus SM21. Out of three recombinant fusants obtained, one (named Fu3) showed higher chitinase production compared to both parents (5 fold increase).