Rhodotorula toruloides for carotenoid production using waste hardwood biomass

Area of Science:

• Biotechnology and Industrial Microbiology
• Sustainable Bioprocessing
• Natural Product Chemistry

Background:

• Urban woody residues are abundant but underutilized biomass resources.
• Carotenoids, such as β-carotene and torulene, are valuable pigments with diverse applications.
• Rhodotorula toruloides is a yeast known for its ability to produce carotenoids.

Purpose of the Study:

• To evaluate urban hardwood pruning residues as feedstocks for carotenoid production by Rhodotorula toruloides.
• To investigate the relationship between the chemical composition of biomass hydrolysates and carotenoid yield.
• To determine the impact of wood extractives on carotenoid biosynthesis.

Main Methods:

• Enzymatic hydrolysis of sessile oak and mulberry tree woods and barks.
• Microbial fermentation of hydrolysates using Rhodotorula toruloides.
• Quantification of total sugars, β-carotene, and torulene.
• Analysis of the effect of extractive removal on yeast growth and carotenoid production.

Main Results:

• Sessile oak bark hydrolysate yielded the highest β-carotene production (362.7 mg/L) and yield (163.4 mg/g DCW).
• Mulberry tree bark hydrolysate provided the highest total sugar concentration (16.4 g/L).
• Removal of inhibitory extractives from woody biomass significantly decreased carotenoid titers, indicating their crucial role in enhancing productivity.

Conclusions:

• Urban woody residues, particularly sessile oak bark, are effective and sustainable feedstocks for microbial carotenoid production.
• Stress-inducing compounds within wood extractives are essential for maximizing carotenoid yield and productivity in Rhodotorula toruloides.
• This study underscores the potential of leveraging urban waste streams for the bio-based production of high-value compounds.