# Black soldier fly protein–based microencapsulation of lemongrass oil improves rumen fermentation efficiency and mitigates methane production in vitro

## TL;DR

Using black soldier fly protein to microencapsulate lemongrass oil improves rumen digestion and reduces methane emissions in a lab setting.

## Contribution

This is the first study to explore black soldier fly protein as a delivery system for essential oils in rumen fermentation.

## Key findings

- Microencapsulated lemongrass oil improved nutrient degradability and gas production kinetics in rumen fermentation.
- Methane production was reduced by up to 48.8% with microencapsulated lemongrass oil at 6% of dry matter.
- The treatment increased beneficial bacteria populations while suppressing methane-producing archaea.

## Abstract

Essential oils (EOs) are promising natural modifiers of rumen fermentation and methane production; however, their volatility and rapid degradation limit their effectiveness. Microencapsulation can shield bioactive compounds and allow controlled release. Insect-derived proteins, especially from black soldier fly (BSF; Hermetia illucens L.), offer a sustainable and functional wall material, yet their use for rumen-targeted delivery remains unexplored. This study aimed to assess the effects of microencapsulated-lemongrass oil (M-LEO) using BSF protein as a biopolymer wall on gas kinetics, nutrient degradability, rumen fermentation parameters, microbial populations, and methane output in vitro.

A completely randomized design was used with five dietary treatments containing M-LEO at 0, 2, 4, 6, and 8% of total dry matter (DM) substrate. In vitro rumen fermentation was performed using rumen fluid from Holstein-crossbred dairy cattle. Fermentation was measured at 12, 24, and 48 h for gas kinetics, in vitro dry matter degradability (IVDMD) and in vitro organic matter degradability (IVOMD), pH, ammonia-nitrogen (NH3-N), volatile fatty acids (VFAs), methane production, and microbial populations quantified by real-time polymerase chain reaction.

M-LEO showed high encapsulation efficiency (85.2%) and significant bioactive content. Supplementing with M-LEO notably improved gas production kinetics and nutrient degradability, with optimal effects at 6% of total DM. At this level, IVDMD and IVOMD increased by up to 11.5% and 10.5%, respectively. Total VFA and propionate concentrations rose significantly (p < 0.05), while acetate proportion and the acetate-to-propionate ratio decreased. Rumen pH and NH3-N levels stayed within optimal ranges and were unaffected by treatment. Methane production was substantially reduced, with decreases of up to 48.8% at 48 h compared to the control. Additionally, M-LEO boosted populations of key cellulolytic bacteria (Fibrobacter succinogenes, Ruminococcus albus, and Ruminococcus flavefaciens) and Megasphaera elsdenii, while significantly suppressing methanogenic archaea (Methanobacteriales).

Microencapsulation of lemongrass oil with BSF protein effectively enhances rumen fermentation efficiency and significantly decreases methane emissions in vitro. This innovative insect-protein delivery system provides a sustainable and climate-friendly feed additive approach, deserving further validation in vivo.