Aims: microalgae use has been recently attracted for the production of biologically active drugs and pharmaceuticals.Carbon source is an essential factor for the Spirulina maxima growth. Since finding the appropriate carbon source and its concentration to achieve high levels of biomass in the shortest cultivation period is very valuable. Therefore, the effect of different carbon sources (sodium carbonate, sodium bicarbonate, glucose and molasses) with different concentrations (16, 24 and 32 gL^-1) on growth and biomass production were evaluated. Methods: Microalgae was grown in 11 treatments with 3 replications at labarotary temperature (28±3 °C) and 1350±100 Lux light intensity (24 hours exposure-time). Maximum specific growth rate and doubling time were calculated according to nonlinear modeling by Wolfram Mathematica software at 99% confidence interval. Findings: The highest biomass concentration (gL^-1) at the highest carbon source concentration in the first 5 days belonged to molasses (3.083), glucose (2.094), sodium carbonate (0.869) and sodium bicarbonate (0.835). Biomass production of treatments except glucose in medium was increased by increasing concentration from 16 to 32 gL^-1. Although molasses has reached on highest biomass production during the first 5 days of cultivation, but the greatest effect on increasing specific growth rate belongs to the glucose sample. Conclusions: As a result, the carbon source and its concentration had a significant effect on the growth and biomass production. Glucose has been selected as an effective carbon source for growth with a concentration of 24gL^-1. Moreover, the highest concentration of treatments had shown the least effect on specific growth rate.

Biosurfactants are metabolites produced by microorganisms which have potential capabilities in various industries due to abundant beneficial properties. In spite of great advantages, commercial utilization of biosurfactants especially in food industry and pharmaceuticals are limited for the reasons of technical and commercial such as low yield, high production cost, and the type of producing strain. Majority of biosurfactant producer microorganisms have ever evaluated, are pathogenic strains which are not acceptable in industrial and environmental utilization particularly in health and cosmetics, pharmaceuticals and food industries. However, the present study aims to investigate high production of cell-bound biosurfactant by lactic acid bacterium Lactobacillus plantarum through optimization of the main carbon source of specific culture medium. Therefore, three culture media with different amount of glucose were evaluated for biomass and biosurfactant (by surface tension reduction of phosphate buffered saline) production in shake flasks and bioreactor (controlled temperature, pH and agitating speed). The results from both shake flasks fermentation and bioreactor showed the maximum biomass concentration of 3.9 and 4.17 g/L, the minimum surface tension of 41.17 and 40.48 mN/m and subsequently the maximum biosurfactant production in culture medium including 30 g/L of glucose, respectively. Furthermore, fourier transform infrared spectroscopy analysis indicated the biosurfactants are structurally a mixture of protein, polysaccharide and possibly phosphate group, possessing glycoprotein structure.