A wild and tolerant yeast suitable for ethanol fermentation from lignocellulose

Area of Science:

• Biotechnology
• Microbiology
• Biochemical Engineering

Background:

• Food waste, rich in starch, presents a viable substrate for bioethanol production.
• Sterilization is often required for efficient fermentation, increasing process costs.
• Existing yeast strains may have limitations in fermenting diverse sugars found in waste streams.

Purpose of the Study:

• To investigate ethanol fermentation from non-sterilized food waste using wild yeast.
• To isolate and identify novel yeast strains capable of fermenting a broader range of monosaccharides for improved bioethanol production.

Main Methods:

• Ethanol fermentation experiments using Issatchenkia orientalis MF-121 on starch-rich food waste without sterilization.
• Isolation of acid- and salt-tolerant yeast strains.
• Fermentation trials with isolated strains using various monosaccharides (glucose, mannose, galactose, fructose, xylose).
• Identification of promising yeast strains using 26S rRNA gene sequencing.

Main Results:

• Issatchenkia orientalis MF-121 demonstrated ethanol production from starch without sterilization.
• A novel yeast strain, Zygoascus hellenicus LK-5G, was successfully isolated.
• Zygoascus hellenicus LK-5G exhibited tolerance to acidic and saline conditions.
• The identified strain efficiently fermented glucose, mannose, galactose, fructose, and notably, xylose to ethanol.

Conclusions:

• Wild yeast can ferment starch to ethanol from food waste under non-sterilized conditions.
• Zygoascus hellenicus LK-5G is a promising candidate for industrial bioethanol production due to its ability to ferment diverse sugars and tolerance to harsh conditions.
• This finding opens avenues for cost-effective bioethanol generation from various lignocellulosic and starchy feedstocks.