Clostridium acetobutylicum has been a focus of research because of its ability to produce high-value compounds that can be used as biofuels. Lignocellulose is a promising feedstock, but the lignin–cellulose–hemicellulose biomass complex requires chemical pre-treatment to yield fermentable saccharides, including cellulose-derived cellobiose, prior to bioproduction of acetone–butanol–ethanol (ABE) and hydrogen. Fermentation capability is limited by lignin and thus process optimization requires knowledge of lignin inhibition. The effects of lignin on cellular metabolism were evaluated for C. acetobutylicum grown on medium containing either cellobiose only or cellobiose plus lignin. Microscopy, gas chromatography and 8-plex iTRAQ-based quantitative proteomic technologies were applied to interrogate the effect of lignin on cellular morphology, fermentation and the proteome. Our results demonstrate that C. acetobutylicum has reduced performance for solvent production when lignin is present in the medium. Medium supplemented with 1 g L−1 of lignin led to delay and decreased solvents production (ethanol; 0.47 g L−1 for cellobiose and 0.27 g L−1 for cellobiose plus lignin and butanol; 0.13 g L−1 for cellobiose and 0.04 g L−1 for cellobiose plus lignin) at 20 and 48 h, respectively, resulting in the accumulation of acetic acid and butyric acid. Of 583 identified proteins (FDR < 1 %), 328 proteins were quantified with at least two unique peptides. Up- or down-regulation of protein expression was determined by comparison of exponential and stationary phases of cellobiose in the presence and absence of lignin. Of relevance, glycolysis and fermentative pathways were mostly down-regulated, during exponential and stationary growth phases in presence of lignin. Moreover, proteins involved in DNA repair, transcription/translation and GTP/ATP-dependent activities were also significantly affected and these changes were associated with altered cell morphology. This is the first comprehensive analysis of the cellular responses of C. acetobutylicum to lignin at metabolic and physiological levels. These data will enable targeted metabolic engineering strategies to optimize biofuel production from biomass by overcoming limitations imposed by the presence of lignin.

Nowadays, proteomics is recognized as one of the fastest growing tools in many areas of research. This is especially true for the study of Saccharomyces cerevisiae, as it is considered to be a model organism for eukaryotic cells. Proteomic analysis provides an insight into global protein expressions from identification to quantitation, from localization to function, and from individual to network systems. Moreover, many methods for identification and quantitation of proteins based on tandem mass spectrometry workflows have recently been developed and widely applied in S. cerevisiae. The current methods and issues in the proteomic analysis of S. cerevisiae are reviewed here.

This study aims at exploring earthworm protein hydrolysate and its peptide fractions as a potential hypoglycemic agent by inhibiting α-amylase and α-glucosidase. Firstly, the best hydrolysis conditions to gain the hydrolysates with the highest α-amylase inhibitory activity (α-AIA) and α-glucosidase inhibitory activity (α-GIA) were figured out using a one-factor test. Next, the stability of the hypoglycemic activity of the hydrolysates and their 5 peptide fractions recovered using ultrafiltration membranes were assessed by employing the tests of in vitro digestion, thermal, and pH treatment. The results showed that at the best hydrolysis conditions, the hydrolysates exhibited α-AIA of 91.30 ± 2.51% and α-GIA of 44.69 ± 0.47%. Specifically, the <1 kDa peptide fraction from the hydrolysate expressed a greater α-AIA than that of acarbose, with nearly the same α-GIA as that of voglibose. The α-AIA and α-GIA of the hydrolysates and their fractions were enhanced after the in vitro digestion treatment, whereas they remained over 40% after the pH treatment in the range of 1 to 11 or heat treatment at 100 °C for 180 min. These data provide the preliminary evidence to develop the earthworm protein hydrolysate and its peptide fractions in functional food or nutraceutical products with hypoglycemic activity.