Novel uses of ensiled biomasses as feedstocks for green biorefineries.

Perennial forage plants are efficient utilizers of solar radiation and nutrients so that there is a lot of scope to increase the production of green biomass in many areas. Currently, grasses are mainly used as feeds for ruminants and equines, but there could be higher added value use for several components of the green biomass. Interest in green biorefining has risen recently motivated by the increased sustainability pressures and need to break the reliance on fossil fuels. Novel products derived from grass, such as paper and packaging, nanofibers, animal bedding, novel protein feeds, extracted proteins, biochemicals, nutraceuticals, bioactive compounds, biogas and biochar could create new sustainable business opportunities in rural areas. Most green biorefinery concepts focus on using fresh green biomass as the feedstock, but preservation of it by ensiling would provide several benefits such as all-year-around availability of the feedstock and increased stability of the press juice and press cake. The major difference between fresh and ensiled grass is the conversion of water soluble carbohydrates into fermentation end products, mainly lactic and acetic acids, that lower the pH of the silage so that it becomes stable in anaerobic conditions. This has some important consequences on the processability and quality of products, which are partly positive and partly negative, e.g., degradation of protein into peptides, amino acids and ammonia. These aspects are discussed in this review.

Preservation characteristics and bacterial communities of crimped ensiled barley grains modulated by moisture content and additive application.

Information about the relationships between preservation characteristics and main bacterial communities of fermented feeds can guide decision making during feed preservation and silage additive development. The objective was to evaluate fermentation quality, aerobic stability, microbial quality and bacterial profile of crimped barley grains ensiled under three moisture contents (MC): 228 (low MC), 287 (medium MC) and 345 (high MC) g/kg fresh matter; and using four additive treatments: 1. Control (CONT), 2. Formic and propionic acid-based additive (FPA), 3. Inoculation with homofermentative and heterofermentative strains of lactic acid bacteria (LAB), and 4. Salt-based additive (SALT). There was a quadratic effect (p < 0.05) of incremental MC on pH where greater decline happened from low (5.81) to medium (4.83) MC than from medium to high (4.28) MC, while lactic acid concentration and aerobic stability increased in a linear manner (p < 0.05). Ammonia-N and acetic acid concentrations increased quadratically (p < 0.05) with increasing levels of MC. The effects of additives depended on MC so that improvements in preservation characteristics in response to LAB and SALT were observed at medium and high MC, while FPA was effective at all MC levels. A minor shift was observed in bacterial ecology from raw material towards low MC samples, with Erwiniaceae sp., Enterobacterales spp. and Pseudomonas dominating the fermentation. A major change occurred in medium and high MC materials, where Fructilactobacillus dominated the fermentation in CONT, FPA and SALT silages. LAB-treated silages at medium and high MC resulted in a distinguished pattern with dominance of Lentilactobacillus followed by Lactiplantibacillus. Most abundant communities in the samples, such as Fructilactobacillus, Erwiniaceae sp., Enterobacterales spp. and Pseudomonas, were correlated with several fermentation characteristics. Our results showed that crimped barley grains could be successfully ensiled under various MC and additive treatments. Low MC feeds had higher risk to be aerobically unstable while high MC resulted in more extensive fermentation, with potentially poor fermentation quality. The suitable additive depends on the raw material characteristics as LAB and SALT require relatively high MC to be effective, while FPA showed consistent improvements over all MC levels used in the current study. Awareness of the MC of grain prior to ensiling allows to identify the risks to preservation quality and provides information for choosing an effective additive.

The bacterial community and metabolome dynamics and their interactions modulate fermentation process of whole crop corn silage prepared with or without inoculants.

Multi-omics approach was adopted to investigate the modulation of bacterial microbiota and metabolome as well as their interactions in whole crop corn ensiling systems by inoculating homofermentative Lactobacillus plantarum or heterofermentative Lactobacillus buchneri. Inoculations of the two different inoculants resulted in substantial differences in microbial community and metabolic composition as well as their dynamics in ensiled corn. Inoculants also altered the correlations of microbiota in different manners, and various keystone species were identified in corn silages with different treatments. Many metabolites with biofunctional activities like bacteriostatic, antioxidant, central nervous system inhibitory and anti-inflammatory were found in the present silage. A constitutive difference in microbiota dynamics was found for several pathways, which were upregulated by specific taxa in middle stage of fermentation, and widespread associations between metabolites with biofunctions and the species of lactic acid bacteria dominated in silage were observed. Multiple microbial and metabolic structures and dynamics were correlated and affected the fermentation process of the corn ensiling systems. Results of the current study improve our understanding of the complicated biological process underlying silage fermentation and provide a framework to re-evaluate silages with biofunctions, which may contribute to target-based regulation methods to produce functional silage for animal production.

Fibrolytic enzyme treatment prior to ensiling increased press-juice and crude protein yield from grass silage.

Grass is a versatile raw material for green biorefineries and preserving it as silage provides a year-round feedstock. The objective of the current study was to evaluate the effect of fibrolytic enzyme application on silage as a feedstock for a biorefinery. Two batches of grass (mixture of timothy and meadow fescue) silages were ensiled in pilot scale after fibrolytic enzyme was applied to them at four levels. Enzyme application increased fibre degradation linearly during ensiling and increased lactic and acetic acid concentrations in the silage. Simultaneously, silage fermentation quality improved as indicated by decreasing pH and ammonia values. Press-juice and crude protein yields increased in response to the fibrolytic enzyme application, which is beneficial in a biorefinery concept for retrieving valuable nutrients from grass matrix. Optimized ensiling methodology can be considered as a pretreatment for a biorefinery process.

A farm-scale grass biorefinery concept for combined pig feed and biogas production.

This study assessed the nutrient flows and the economic viability of a farm-scale grass biorefinery concept for a pig farm. Grass silage was separated into liquid and solid fractions; the liquid fraction was used as pig feed and the solid fraction was directed to biogas production together with pig slurry. The addition of grass to the farm's crop rotation and its use in feed and biogas production slightly increased the share of nitrogen (N) circulating within the farm (by 2%), thus decreasing phosphorus circulation by 3%. Despite the positive effect on N balance, the economy of the farm-scale concept had challenges. However, upgrading biogas to vehicle fuel and selling it on farm was more economically viable than combined heat and power production. The proposed concept could be economically viable with a slight increase in the price of vehicle fuel, a moderate increase in the price of the grass liquid fraction, or better optimization of the system, starting with grass cultivation and processing. Moreover, profitable production could also be reached by increasing the scale of production by increasing farm size or by two or more farms working together.

Effects of contrasting concentrate feeding strategies on meat quality of growing and finishing dairy bulls offered grass silage and barley based diets.

The objective was to examine the effects of concentrate level (barley grain 39 and 74 g dry matter/kg0.60 live weight) and allocation regime (steady, increased, decreased) on meat quality of growing dairy bulls fed grass silage ad libitum. Chemical, instrumental and sensory analyses were used for measuring quality of longissimus lumborum (LL). Greater concentrate level increased fat content (P = 0.035) and tenderness of sensory analysis (P = 0.009) of LL but did not affect pH, colour, drip loss, sarcomere length, shear force, juiciness or flavour. Periodic concentrate allocation reduced drip loss (P = 0.046) and tenderness (P = 0.001) compared to steady feeding. Observed effects on meat quality were minor and one explanation for this might be low carcass and meat fat content in all treatments. The experiment demonstrated the ability of growing bulls to adapt to different feeding regimes without major effects on meat quality, but simultaneously highlighted the challenge to affect beef quality by practically feasible diets.