## 4 Discussion  
This study is the first report on the nutrient and phytochemical characterisation of hempeseed screenings. Moreover, this is the first detailed report on the fermentability and microbial metabolism in vitro using human mixed microbiota of a hempesed by-product. Our results indicated that hempesed by-products, such as hemp screenings used in the current study, were a rich source of nutrients in terms of protein, dietary fibre and fat. Moreover, the hemp screenings were particularly rich in tryptophan, an essential amino acid needed for general growth and development, the production of niacin (vitamin B3), and the neurotransmitter serotonin. Considering that the reference dietary intake (RDI) for tryptophan is 4 mg per kilogram of body weight, a person weighing 70 Kg should consume a minimum of 10 g of screenings to meet the RDI for tryptophan (280 mg of tryptophan per day). Insoluble fibre is the dominant fibre in hempesed screenings, comprising 98% of the total NSP measured. This study revealed that the hemp screening fibre was highly fermentable, resulting in high amounts of SCFA, including acetate, propionate, and butyrate, with a significant increase in acetate (\(p<0.05\)), propionate (\(p<0.001\)), and butyrate (\(p<0.01\)) measured following microbial fermentation of the hempesed screenings with human mixed microbiota in vitro. Moreover, there was no overall effect on microbial formation of SCFA after bioprocessing, and therefore, hemp screening fibre remained highly fermentable. These findings suggest the potential use of hempesed screenings as a functional ingredient in foods. Furthermore, these results encourage the adoption of the hemp screenings as a habitual source of nutrients to diversify the fibre composition of the human diets. It is  
Figure 4: Short-chain fatty acids (SCFA) production over 72 h fermentation as incremental change (mM) in concentration, average \(\pm\) STD (\(n=3\)). The raw and enzyme-treated hempesed screenings (EM_1 and EC_2), as well as their IVDG-predigested samples, were inoculated with faecal slurries from each of the three donors (Donor 1, 2 and 3). Values were calculated by subtracting the value of 0 h from the value of the fermented sample at 72 h for each sample. Statistical analysis was evaluated by either one-way ANOVA with [PERSON]’s tests for multiple comparisons or \(t\)-test between two groups (with or without IVDG). as important to boost the dietary fibre content and diversify the fibre source and ensure that the fibre source is fermentable because of the numerous health benefits attributed to SCFAs production during fermentation, as these weak acids play an important role in the maintenance of gut and metabolic health [38]. Hemspeed screenings are also a rich source of phenolic molecules, summing, on average, 375.09 mg/Kg of 129 molecules measured by LC-MS/MS analysis. The bioprocessing treatments had a significant effect on the extractability of these molecules, the total amount almost doubled after the BY_2 treatment to 635.47 mg/Kg (_p_ < 0.01). Other bioprocessing treatments with significant impact on the extractability of phenolics molecules were EC2 with 583.08 mg/kg (_p_ < 0.01), EM2 with 581.03 mg/Kg (_p_ < 0.01) and BY+EC2 with 591.71 (_p_ < 0.001). Springaresinol was the most abundant molecule measured in the hemp screenings, almost exclusively in the bound form being released after acid hydrolysis. The extractability of syringaresinol was not affected by any of the bioprocessing treatments. This suggests that syringaresinol is likely to remain bound through early gastrointestinal (GI) digestion and be released in the colon, where it can be metabolised by the gut microbiota. Indeed, the results of the microbial incubations of the hempseed screenings showed enterolactone was one of the metabolites that increased during the incubations. Lignans, such as enterolactone, are considered human health-promoting molecules [39], thus, dietary intake of lignan-rich foods could be a useful way to sustain the prevention of chronic illness.