Semisolid fermentation of ryegrass straw

Area of Science:

• Agricultural Science
• Microbiology
• Biotechnology

Background:

• Ryegrass straw is an abundant agricultural byproduct with potential for bioconversion.
• Pretreatment and microbial fermentation can improve the nutritional quality of lignocellulosic materials.

Purpose of the Study:

• To evaluate the efficacy of microbial fermentation using Candida utilis, Aureobasidium pullulans, and Trichoderma viride on pretreated ryegrass straw.
• To determine the optimal pretreatment conditions for enhancing straw's nutritional content and digestibility.

Main Methods:

• Ryegrass straw was pretreated via hydrolysis with sulfuric acid (H2SO4) at varying temperatures (121°C, 100°C, room temperature) and pH adjusted with ammonium hydroxide (NH4OH).
• Fermentation was conducted using selected microorganisms on a semi-solid substrate with 75% moisture for 2-3 days at room temperature.
• Nutritional analysis focused on sugar, nitrogen (N), protein, crude fat, and digestibility.

Main Results:

• Pretreatment at 121°C yielded straw with 30% sugar and 2.3% N.
• Microbial growth increased 20- to 200-fold within 18-42 hours of incubation.
• Fermentation resulted in a fourfold increase in protein, a fivefold increase in crude fat, and a 40% increase in straw digestibility.

Conclusions:

• Microbial fermentation significantly improves the nutritional profile and digestibility of pretreated ryegrass straw.
• Candida utilis grown on straw pretreated at 121°C demonstrated the most substantial increases in protein content and digestibility.
• This process offers a viable method for upgrading agricultural residues into valuable feed components.