Feedstock blending as a strategy for hydrothermal liquefaction: lipid-rich scum from primary sedimentation and wastewater sludge

One salient advantage of hydrothermal liquefaction (HTL) is the ability to process diverse feedstocks individually or as blends. This creates an opportunity for using wet organic waste feedstocks that in many cases pose a disposal liability. The low cost associated with the feedstock enables cost-effective deployment of smaller, decentralized processing plants that match the geographic availability of wet waste resources. Two underutilized sources of wet waste biomass are wastewater sludge and fats, oils, and greases (FOG). In the United States, these each represent about 20% of the total HTL biocrude production potential from wet wastes. In this study, the selected FOG stream is decanted scum from the primary sedimentation operation of the same wastewater treatment plant (WWTP) that provided the sludge. Among the types of FOG, wastewater scum is one of the more complex and challenging. Scum contains entrained water, plant matter like leaves and seeds, and bits of garbage (paper and plastic). For most other processes to access the lipids in scum, some combination of heating, filtering, and solvent extraction would be required, leading to costly and/or inefficient recovery. HTL is preferable because it is a wet process and the scum can be blended directly to capture the whole energy content in the blended feed. Using a blend of primary and secondary sludge from Central Contra Costa Sanitary District (CCCSD) and decanted scum from CCCSD primary sedimentation as the source of FOG, a blend of sludge and scum was successfully prepared and processed in a bench scale continuous flow HTL system. A total of 54 L of blended slurry was converted to 4.2 L of biocrude oil. The scum was blended with the sludge such that it represented 20 wt% of the total dry, ash-free (daf) solids in the feed. The resulting biocrude had a much lower density (0.95 g/cm3) than the biocrude from CCCSD sludge alone (0.99 g/cm3) leading to improved gravity separation from the aqueous phase. The biocrude was also lower in moisture. During the oral presentation, the focus will be on the process of feedstock selection, evaluation, and characteristics including detailed steps and equipment used to format the blended feedstock for use in the HTL reactor system. The poster will include data for the integrated process including mass balance, yields, and characterization of products

FOX-2 Dependent Splicing of Ataxin-2 Transcript Is Affected by Ataxin-1 Overexpression

Alternative splicing is a fundamental posttranscriptional mechanism for controlling gene expression, and splicing defects have been linked to various human disorders. The splicing factor FOX-2 is part of a main protein interaction hub in a network related to human inherited ataxias, however, its impact remains to be elucidated. Here, we focused on the reported interaction between FOX-2 and ataxin-1, the disease-causing protein in spinocerebellar ataxia type 1. In this line, we further evaluated this interaction by yeast-2-hybrid analyses and co-immunoprecipitation experiments in mammalian cells. Interestingly, we discovered that FOX-2 localization and splicing activity is affected in the presence of nuclear ataxin-1 inclusions. Moreover, we observed that FOX-2 directly interacts with ataxin-2, a protein modulating spinocerebellar ataxia type 1 pathogenesis. Finally, we provide evidence that splicing of pre-mRNA of ataxin-2 depends on FOX-2 activity, since reduction of FOX-2 levels led to increased skipping of exon 18 in ataxin-2 transcripts. Most striking, we observed that ataxin-1 overexpression has an effect on this splicing event as well. Thus, our results demonstrate that FOX-2 is involved in splicing of ataxin-2 transcripts and that this splicing event is altered by overexpression of ataxin-1

Excitability of the T-tubular system in rat skeletal muscle: roles of K(+) and Na(+) gradients and Na(+)-K(+) pump activity

Strenuous exercise causes an increase in extracellular [K(+)] and intracellular Na(+) ([Na(+)](i)) of working muscles, which may reduce sarcolemma excitability. The excitability of the sarcolemma is, however, to some extent protected by a concomitant increase in the activity of muscle Na(+)–K(+) pumps. The exercise-induced build-up of extracellular K(+) is most likely larger in the T-tubules than in the interstitium but the significance of the cation shifts and Na(+)–K(+) pump for the excitability of the T-tubular membrane and the voltage sensors is largely unknown. Using mechanically skinned fibres, we here study the role of the Na(+)–K(+) pump in maintaining T-tubular function in fibres with reduced chemical K(+) gradient. The Na(+)–K(+) pump activity was manipulated by changing [Na(+)](i). The responsiveness of the T-tubules was evaluated from the excitation-induced force production of the fibres. Compared to control twitch force in fibres with a close to normal intracellular [K(+)] ([K(+)](i)), a reduction in [K(+)](i) to below 60 mm significantly reduced twitch force. Between 10 and 50 mm Na(+), the reduction in force depended on [Na(+)](i), the twitch force at 40 mm K(+) being 22 ± 4 and 54 ± 9% (of control force) at a [Na(+)](i) of 10 and 20 mm, respectively (n = 4). Double pulse stimulation of fibres at low [K(+)](i) showed that although elevated [Na(+)](i) increased the responsiveness to single action potentials, it reduced the capacity of the T-tubules to respond to high frequency stimulation. It is concluded that a reduction in the chemical gradient for K(+), as takes place during intensive exercise, may depress T-tubular function, but that a concomitant exercise-induced increase in [Na(+)](i) protects T-tubular function by stimulating the Na(+)–K(+) pump