Production of Lactic Acid from Lipid Extracted Algal Biomass of Scenedesmus sp.

Abstract

Biorefining process was developed for the utilization of lipid extracted algal biomass (LEAB) of Scenedesmus sp. Carbohydrate rich LEAB was hydrolyzed by different acids (HNO₃, H₂SO₄, H₃PO₄, HClO₄, HCl) and alkali (NaOH, KOH) to yield fermentable sugars for bioconversion into lactic acid. Treatment with 0.9 M H₂SO₄ at 121 °C for 5 min was ideal for the release of reducing sugar (7.41 ± 0.56 g/L), corresponding to a saccharification efficiency of 37.03 ± 2.81%, with minimum generation of inhibitors, furfural and 5-hydroxymethyl furfural. LEAB-derived acid hydrolysate was neutralized by calcium hydroxide and supplemented with organic nitrogen sources (peptone, beef extract and yeast extract), prior to fermentation by Lactobacillus casei to transform reducing sugars into lactic acid. Peptone supplementation showed maximum 68.83 ± 0.43% conversion of reducing sugar into 1.2 g/L lactic acid, achieving a lactic acid yield of 0.81 ± 0.0042 g/g. These results highlight the strong potential of LEAB as a sustainable feedstock for lactic acid production in biorefineries and its application in food industry as preservative and acidulant, cosmetics and biodegradable polymers such as polylactic acid (PLA).