Green extraction of agar from Hypnea pannosa seaweed: A comparative study of different techniques and optimization using response surface methodology

This study aimed to evaluate the optimal method for extracting agar from Hypnea pannosa seaweed and assess its purity and yield. Agar is a hydrocolloid found in red seaweeds and used in various industries such as food, cosmetics, and medicine. Three different extraction methods were employed for this study, namely ultrasoundassisted extraction (UAE), microwave-assisted extraction (MAE), and ultrasound microwave-assisted extraction (UMAE), each using varying power levels and extraction times. A central composite Response surface methodology (RSM) design was used to compare these methods. Results showed that UAE had the highest extraction yield at 32.99 %, followed by MAE, UMAE, and conventional methods at 27.04 %, 26.19 %, and 12 %, respectively. Various techniques were used to evaluate agar quality, including spectral analysis (FT-IR), gel strength, viscosity, 3,6 anhydrous L galactose (AG), and sulfate content. Samples treated with ultrasound had higher-quality agar than those treated with other methods, with significantly better gel strength, 3,6 AG content, viscosity, and lower sulfate content. Gel strength was 485.50 +/- 4.27 g cm(-2), 3,6 AG content was 62.89 +/- 2.89%, viscosity was 48.32 +/- 0.03 centipoises and sulfate content was 1.32 +/- 0.02 % in UAE. FT-IR analysis confirmed the presence of functional groups in the fingerprint region of identification for polysaccharides in UAE agar. UAE (30 min, 60 % amplitude) was identified as the most viable green extraction technology, offering superior extraction yield and agar quality compared to the other treatments. Using green extraction techniques in obtaining agar has significant implications for the sustainable production of natural products. This research also highlights the potential application of agar in the skincare or pharmaceutical industry, paving the way for developing eco-friendly products. Overall, this study suggests that UAE is an efficient method for extracting agar from H. pannosa and has novel applications in nutraceuticals and cosmeceuticals. Novelty impact statement: The current study presents a comprehensive investigation of the green extraction of agar from Hypnea pannosa seaweed using different techniques, along with optimization through response surface methodology. T he novelty of this research lies in its focus on sustainable and eco-friendly extraction methods, which are increasingly gaining importance in the current global scenario. The comparative study on the different techniques used for the extraction of agar provides a critical evaluation of the advantages and limitations of each method. The use of response surface methodology in the optimization process is a noteworthy feature, as it allows for the identification of optimal extraction conditions with greater accuracy and reliability. The findings of this study significantly contribute to the development of sustainable practices in the seaweed industry, and its academic value is undeniable.