Synthetic surfactants are becoming increasingly unpopular in many applications due to previously disregarded effects on biological systems and this has led to a new focus on replacing such products with biosurfactants that are biodegradable and produced from renewal resources. Microbially derived biosurfactants have been investigated in numerous studies in areas including: increasing feed digestibility in an agricultural context, improving seed protection and fertility, plant pathogen control, antimicrobial activity, antibiofilm activity, wound healing and dermatological care, improved oral cavity care, drug delivery systems and anticancer treatments. The development of the potential of biosurfactants has been hindered somewhat by the myriad of approaches taken in their investigations, the focus on pathogens as source species and the costs associated with large‐scale production. Here, we focus on various microbial sources of biosurfactants and the current trends in terms of agricultural and biomedical applications.

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Background Brown seaweeds are known to be a rich source of fiber with the presence of several non-digestible polysaccharides including laminarin, fucoidan and alginate. These individual polysaccharides have previously been shown to favorably alter the gut microbiota composition and activity albeit the effect of the collective brown seaweed fiber component on the microbiota remains to be determined. Methods This study investigated the effect of a crude polysaccharide-rich extract obtained from Laminaria digitata (CE) and a depolymerized CE extract (DE) on the gut microbiota composition and metabolism using an in vitro fecal batch culture model though metagenomic compositional analysis using 16S rRNA FLX amplicon pyrosequencing and short-chain fatty acid (SCFA) analysis using GC-FID. Results Selective culture analysis showed no significant changes in cultured lactobacilli or bifidobacteria between the CE or DE and the cellulose-negative control at any time point measured (0, 5, 10, 24, 36, 48 h). Following metagenomic analysis, the CE and DE significantly altered the relative abundance of several families including Lachnospiraceae and genera including Streptococcus, Ruminococcus and Parabacteroides of human fecal bacterial populations in comparison to cellulose after 24 h. The concentrations of acetic acid, propionic acid, butyric acid and total SCFA were significantly higher for both the CE and DE compared to cellulose after 10, 24, 36 and 48 h fermentation (p < 0.05). Furthermore, the acetate:propionate ratio was significantly reduced (p < 0.05) for both CD and DE following 24, 36 and 48 h fermentation. Conclusion The microbiota-associated metabolic and compositional changes noted provide initial indication of putative beneficial health benefits of L. digitata in vitro; however, research is needed to clarify if L. digitata-derived fiber can favorably alter the gut microbiota and confer health benefits in vivo.

Four, 4-week old Friesian calves (BW=50±3 kg), fitted with duodenal, portal and jugular catheters and duodenal electrodes, were used to study the metabolism of duodenally infused betaine (Bet) or choline (Chol) and their effects on blood sulphur amino acids and duodenal myoelectrical migrating complexes (MMC). Animals were fed milk replacer at 5% BW twice daily, but were starved overnight prior to the experimental procedure. Animals received a saline infusion for 2 h at 1 ml/min followed by a 1 h infusion of 1·2 or 3·6 mmol of either Bet or Chol. Infusion of saline was continued for another 2 h after the cessation of the amino acid infusion. Duodenal MMC were measured with a computer-based data acquisition system (MacLab, ADI, Australia). There were no differences in measured blood metabolites between the jugular and portal vein; therefore, only average values were presented. Plasma Met concentrations increased from 20 μm, 20 min after initiating Bet infusion, whereas a lower dose of Chol decreased plasma Met and a higher one had no effect. The highest plasma methionine (Met) concentration (29 μm) occurred 45 min after the onset of the Bet infusion (1·2 mmol). Compared to the 3·6 mmol Bet infusion, the intraduodenal infusion of 1·2 mmol of Bet resulted in a greater area (P<0·001) under the plasma Met concentration curve (281·6 v. 73·3 mmol). A similar pattern was observed for plasma cystine concentrations. Infusion of Bet or Chol did not change the duration of MMC but Bet increased the number of spikes during the phase of low spiking activity (37·5 v. 14·6 pre-infusion, spikes/min; P<0·01). Chol had the same effect but only after the infusion ceased (29·3 v. 11·5 spikes/min; P<0·01). The velocity of migration of regular spiking activity (RSA; related to digesta transport) increased as a result of infusion (16·4 pre-infusion v. 31·3 Bet, 25·2 Chol cm/min; P<0·01). Chol caused an immediate increase in the velocity of migration of RSA, whereas with the Bet infusion an increase was observed after cessation of infusion. Increased concentrations of sulphur amino acids during Bet infusion could indicate that labile methyl groups may be limited in calves. Postruminal Bet and Chol supplementation may cause a decrease in nutrient absorption in the small intestine by increasing digesta transport.

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