Microbial lipid production by Cryptococcus curvatus from vegetable waste hydrolysate

Area of Science:

• Biotechnology and Bioengineering
• Renewable Energy Sources
• Waste Valorization

Background:

• Vegetable waste (VW) presents a significant disposal challenge.
• Efficiently converting VW into valuable products like biofuels is crucial for sustainability.
• Pre-treatment methods are key to unlocking sugars from lignocellulosic biomass.

Purpose of the Study:

• To evaluate the efficacy of various acid and alkali pre-treatments on releasing reducing sugars (RS) from vegetable waste.
• To assess the suitability of pre-treated vegetable waste hydrolysates (PT-VWH) for microbial lipid production using yeast fermentation.
• To analyze the fatty acid profile of the produced lipids for potential biodiesel applications.

Main Methods:

• Vegetable waste was pre-treated with different concentrations (0.5-2.0%) of sulfuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), phosphoric acid (H3PO4), sodium hydroxide (NaOH), and potassium hydroxide (KOH).
• Reducing sugar yield was quantified after pre-treatment.
• Pre-treated vegetable waste hydrolysates were used for yeast fermentation with Cryptococcus curvatus MTCC 2698 to produce biomass and lipids.
• Fatty Acid Methyl Ester (FAME) profiling was performed on the extracted lipids.

Main Results:

• The highest reducing sugar yields were obtained using 1.5% H2SO4 (472.36 ± 1.89 g/l) and 2% HCl (439.13 ± 1.04 g/l).
• Maximum yeast biomass (9.46 ± 0.1 g/l) and lipid content (28.3 ± 0.5%) were achieved with 1.5% H2SO4 PT-VWH.
• Yeast grown on 2% HCl PT-VWH yielded 8.12 ± 0.1 g/l biomass and 26 ± 0.5% lipid.
• FAME profiling indicated a predominance of palmitic, stearic, oleic, and linoleic acids, beneficial for biodiesel quality.

Conclusions:

• Acid pre-treatment, particularly with sulfuric and hydrochloric acids, is effective for releasing reducing sugars from vegetable waste.
• Pre-treated vegetable waste hydrolysates support significant yeast biomass and lipid production.
• The fatty acid composition of the yeast lipids suggests suitability for biodiesel production, contributing to waste valorization and renewable energy goals.