Micro-assay method for enzymatic saccharification of industrially relevant lignocellulose substrates
BIOMASS CONVERSION AND BIOREFINERY
Authors: Pengilly, C.; Garcia-Aparicio, M.; Swart, J. P. J.; Gorgens, J. F.
Abstract
The development of micro-assays suitable for automation systems represents a helpful alternative by which many enzymes and factors can be studied simultaneously for the conversion of lignocellulose. The purpose of the present study was to evaluate a micro-assay method, based on hand-sheets, to reproducibly aliquot-pretreated lignocellulosic biomass at milligramme scale with minimal impact on the digestibility of the material. To favour representative sampling and handling for enzymatic conversion at milligramme scale, the solid fractions from steam-pretreated sweet sorghum bagasse (SSB) and triticale straw (TS) were subjected to homogenisation steps in sequential disintegrator and liquidiser at different severities prior to hand-sheet making (TAPPI). In the case of SSB, the disintegrator treatment (37,500 rpm) was sufficient to obtain the required fibre lengths, while the combined treatment with liquidiser (6250 rpm) and disintegrator (31,250 rpm) was needed for TS. The selected steps were able to improve homogenisation and fibre size distribution in the hand-sheets, attaining the required fibre lengths (less than 8 mm), with minimal influence on glucan conversion when using a conventional enzyme cocktail. The combined treatment and hand-sheet making had a more pronounced effect on the conversion of the xylan, with reduced xylose yields compared to small scale. The carbohydrate conversion in micro-assay was susceptible to more efficient enzyme combinations depending on the structural properties of the pretreated materials, presence and concentration of inhibitors as well as the enzyme dosage used. Nevertheless, the micro-assay method could distinguish between the different enzyme combinations, identifying those resulting in higher sugar yields from different lignocellulose materials pretreated under relatively mild conditions.
Transcranial Direct Current Stimulation of the Medial Prefrontal Cortex Has No Specific Effect on Self-referential Processes
FRONTIERS IN HUMAN NEUROSCIENCE
Authors: Mainz, Verena; Britz, Sara; Forster, Saskia Doreen; Drueke, Barbara; Gauggel, Siegfried
Abstract
The processing of self-referential information can be influenced by transcranial magnetic stimulation (TMS). The present randomized controlled study investigated whether similar effects can be elicited through the application of transcranial direct current stimulation (tDCS) regarding the "self-serving bias" (SSB) and the "mnemic neglect effect" (MNE). Seventy-five healthy males (M-age = 25; SD = 4.3) were investigated in a between-groups design with random assignment by applying anodal, cathodal, or sham tDCS to the medial prefrontal cortex (mPFC). After stimulation, the participants judged if 80 personality traits (40 positive, 40 negative) were self-descriptive or not. Finally, the participants had to recall the previously presented adjectives. All three stimulation groups showed the expected SSB and MNE. Still, and contrary to our hypotheses, tDCS revealed neither a significant interaction effect between groups and valence concerning the number of chosen self-referential traits (F-(2,F-72) = 1.36, p = 0.26, eta G2 = 0.02) nor an interaction effect between groups, valence, and self-reference concerning the percentage of recalled words (F-(2,F-71) = 0.69, p = 0.50, eta G2 = 0.01). However, a post hoc inspection of effect sizes revealed that less negative traits were indicated as self-referential in the anodal compared to the cathodal group (ES: -0.59; CI: -1.16 to -0.03). Moreover, the participants showed-regardless of self-reference and type of stimulation-a better recall with tDCS in comparison to sham stimulation. Our results indicate that tDCS of the mPFC in healthy young men has no influence on the SSB and the MNE. However, tDCS seems to improve memory performance.