Sulfate-rich polysaccharides from microalgae as biostimulants for enhanced xanthan gum production by Xanthomonas campestris

چکیده مقاله

Xanthan gum is a high-value microbial exopolysaccharide widely used in food, pharmaceutical, and oil recovery industries due to its good rheological properties. Conventional xanthan gum production relies on costly refined carbon sources. The use of biostimulants to enhance microbial fermentation has emerged as a promising strategy to improve product yield and reduce production costs. This study investigated a sustainable alternative by evaluating polysaccharides extracted from four microalgal species—Geitlerinema sp., Spirulina platensis, Chlorella vulgaris, and Dunaliella salina—as biostimulants for xanthan production by Xanthomonas campestris. The experimental design involved an initial screening of all four polysaccharides at 0.05 g/L, followed by optimization of the selected Geitlerinema sp. polysaccharide at 0.05–0.6 g/L. All fermentations were carried out at 30 ◦C, 180 rpm, for 72 h. The polysaccharide from Geitlerinema sp., characterized by its high sulfate content (8.147 mg/g) and high C/N ratio (17.6), was identified as the most effective biostimulant among the four tested species (p < 0.05). Optimization achieved a xanthan yield of 18.53 g/L, a 140% increase over the control (p < 0.05). The product exhibited commercial-grade quality, with satisfactory pyruvate content and viscosity. A consistent relationship between sulfate content and xanthan yield was observed, indicating a potential relationship relevant to the biostimulant activity. The present work establishes algal-derived polysaccharides, particularly from Geitlerinema sp., as potent, sustainable biostimulants that can transform industrial biopolymer production, aligning with circular bioeconomy principles.