Maximizing biofuel production from algal biomass: A study on biohydrogen and bioethanol production using Mg-Zn ferrite nanoparticles

Algal biomass is a promising renewable feedstock for biofuel production that does not compete with food crops or require complex pretreatment like lignocellulosic biomass. This study examined biofuel production from two algae: Alkalinema pantanalense (cyanobacteria) and Chlorella vulgaris (green alga). Although there was no significant difference in their biomass, A. pantanalense showed a higher carbohydrate content (204.96 mg L-1 ) than C. vulgaris (156.07 mg L-1 ). To maximize reducing sugar release, three pretreatments were tested: thermotacidic, biological using the new fungal isolate Trichoderma longibrachiatum , and biological with nanoparticles. Biological pretreatment with Mg - Zn ferrite nanoparticles (MZF-nps) at 60 mg L-1 concentration gave the best results, significantly enhancing cellulase, beta-glucosidase and filter paper cellulase activities by 20.94 % ( A. pantanalense ) and 18.63 % ( C. vulgaris ). For biohydrogen production, the co-culture of Klebsiella pneumoniae and Enterobacter cloacae resulted in faster fermentation and improved hydrogen evolution compared to individual cultures. A. pantanalense and C. vulgaris yields were 35.1 mL g-1 and 26.6 mL g-1 dry weight, with maximal cumulative production of 2478 mL L-1 and 1845 mL L-1 , respectively. Optimized Saccharomyces cerevisiae bioethanol fermentation conditions included 72 h incubation, 5 % inoculum, 30 degrees C, pH 5 under shaking condition, yielded 11.2 g L-1 ( A. pantanalense ) and 7.2 g L-1 ( C. vulgaris ). Furthermore, MZF-nps hydrolysate significantly increased bioethanol production, by 4.2-fold ( A. pantanalense ) to 32.45 g L-1 and 3.48-fold ( C. vulgaris ) to 28.6 g L-1 , compared to thermoacidic pretreatment. In summary, biological pretreatment demonstrates the potential of algal biomass as a renewable feedstock for sustainable biofuel production.