Targeted microbial ensilage additives for Laminaria digitata and Saccharina latissima

Abstract

Seaweeds are a potential feedstock for biofuel and biochemical production. However, seaweed biomass is subject to rapid degradation. This project aims at evaluating the prospect of using microbial additives in an ensiling process for the preservation of the brown seaweed Laminaria digitata and Saccharina latissima. Lactic acid bacteria (LAB) isolated from seaweed silage may be suitable as microbial ensilage additives as they thrive in that type of environment. Seven bacterial strains were isolated from seaweed silage of the species L. digitata, and were determined to belong to the genus Lactobacillus. The bacterial isolates were screened for growth on the carbohydrates laminarin and mannitol, which are storage carbohydrates in the kelp species of interest. The results from the screening showed that the isolates grew on mannitol but not on laminarin. Two strains were selected for further investigation of products formed during growth on mannitol. The main products formed for both strains were lactate and acetate. In continuation, these strains were tested as microbial ensilage additives for S. latissima and L. digitata. The effectiveness of the strains as ensilage additives was compared to a chemical additive and ensiling without additives. Biomass retention was monitored over the course of the ensiling assuming biomass loss as gases was due to unwanted fermentation. The isolates had a positive effect retaining 1 % more biomass, compared to ensiling without any additives. However, there was no significant difference between the two stains. Furthermore, the isolates were slightly outperformed by the chemical additive.