The protein fraction from wheat-based dried distiller's grain with solubles (DDGS): extraction and valorization

High-Efficiency Conversion of Bread Residues to Ethanol and Edible Biomass Using Filamentous Fungi at High Solids Loading: A Biorefinery Approach

Bread residues represent a significant fraction of retail food wastes, becoming a severe environmental challenge and an economic loss for the food sector. They are, however, an attractive resource for bioconversion into value-added products. In this study, the edible filamentous fungi Neurospora intermedia and Aspergillus oryzae were employed for the production of bioethanol and high-protein biomass by cultivation on enzymatically liquefied bread-waste medium at 150 g/L solids. The fermentation of hydrolysate by N. intermedia resulted in the ethanol titer of 32.2 g/L and biomass yield of 19.2 g/L with ca. 45% protein. However, the fermentation ended with a considerable amount of residual fermentable sugars; therefore, the liquid medium after the first fermentation was distilled and fermented again by two fungal strains (N. intermedia and A. oryzae). The fermentations resulted in the production of additional ethanol and biomass. A. oryzae showed better performance in the production of biomass, while the other strain yielded more ethanol. The final products’ yield ranged 0.29–0.32 g EtOH/g and 0.20–0.22 g biomass/g bread waste depending on the strain used in the second fermentation. The study shows that valorization of bread residuals by fungi is a promising option for the production of biofuels and foodstuff within the circular bioeconomy approach.

Resource Recycling Utilization of Distillers Grains for Preparing Cationic Quaternary Ammonium—Ammonium Material and Adsorption of Acid Yellow 11

Using distillers grains (DG) as raw material after pre-treatment with sodium hydroxide (NaOH) and modified with cationic etherification agent 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC), cationic quaternary ammonium distillers grains adsorption material (CDG) was successfully prepared. The optimal adsorption conditions were an adsorption temperature of 25 °C, adsorption time of 180 min, amount of adsorbent at 8.5 g/L, initial dye concentration of 100 mg/L, and pH of dye solution 7.0. The structure of CDG was characterized by FTIR, EDS, SEM, BET, ultraviolet spectrum analysis, and analysis of the zeta potential, while the adsorption mechanism was studied by adsorption kinetics, isotherms, and thermodynamics. The results showed that CHPTAC modified the distillers grains successfully and induced the formation of CDG with a large number of pore structures and good adsorption effect. The highest adsorption yield was above 98%, while after eight rounds of adsorption–desorption experiments, the adsorption rate was 81.80%. The adsorption mechanism showed that the adsorption process of acid yellow 11 (AY11) by CDG conforms to the pseudo-second-order kinetic model, mainly with chemical and physical adsorption such as pore adsorption and electrostatic adsorption. Thermodynamics conforms to the Freundlich isothermal model, and the adsorption process is a spontaneous, endothermic and entropy-increasing process.

Value-Added Products from Ethanol Fermentation—A Review

Global demand for renewable and sustainable energy is increasing, and one of the most common biofuels is ethanol. Most ethanol is produced by Saccharomyces cerevisiae (yeast) fermentation of either crops rich in sucrose (e.g., sugar cane and sugar beet) or starch-rich crops (e.g., corn and starchy grains). Ethanol produced from these sources is termed a first-generation biofuel. Yeast fermentation can yield a range of additional valuable co-products that accumulate during primary fermentation (e.g., protein concentrates, water soluble metabolites, fusel alcohols, and industrial enzymes). Distillers’ solubles is a liquid co-product that can be used in animal feed or as a resource for recovery of valuable materials. In some processes it is preferred that this fraction is modified by a second fermentation with another fermentation organism (e.g., lactic acid bacteria). Such two stage fermentations can produce valuable compounds, such as 1,3-propanediol, organic acids, and bacteriocins. The use of lactic acid bacteria can also lead to the aggregation of stillage proteins and enable protein aggregation into concentrates. Once concentrated, the protein has utility as a high-protein feed ingredient. After separation of protein concentrates the remaining solution is a potential source of several known small molecules. The purpose of this review is to provide policy makers, bioethanol producers, and researchers insight into additional added-value products that can be recovered from ethanol beers. Novel products may be isolated during or after distillation. The ability to isolate and purify these compounds can provide substantial additional revenue for biofuel manufacturers through the development of marketable co-products.

Simultaneous saccharification and fermentation of native rye, wheat and triticale starch

BACKGROUND

The increasing global demand for starchy raw material requires new methods for obtaining ethanol from a range of plants using environmentally friendly methods. Granular starch-hydrolyzing enzymes (GSHE) can effectively support the development of the distillery industry.

RESULTS

The aim of this study was to evaluate the effectiveness of simultaneous saccharification and fermentation of native rye, wheat or triticale starch. Mashes were prepared using methods that limit water and energy consumption (pre-hydrolysis at 35 °C for 30 min). The results show that the degree of starch saccharification depended on the raw material. However, the highest yields of ethanol were obtained with 100 kg of triticale mashes (38.9 ± 1.4 L absolute alcohol) as compared to rye and wheat mashes. The concentration of dry matter (between 250 and 280 g L^-1 ) in the mashes was not associated with a decrease in ethanol yield and improved efficiency in the case of wheat and triticale.

CONCLUSION

Simultaneous saccharification and fermentation offers a low-cost and environmentally friendly alternative to existing procedures for industrial ethanol production, which may be of particular interest to raw-spirit producers, as well as to the food and fermentation industry at large. © 2019 Society of Chemical Industry.

Microbial production of d-lactic acid from dried distiller's grains with solubles

d-Lactic acid production is gaining increasing attention due to the thermostable properties of its polymer, poly-d-lactic acid . In this study, Lactobacillus coryniformis subsp. torquens, was evaluated for its ability to produce d-lactic acid using Dried Distiller's Grains with Solubles (DDGS) hydrolysate as the substrate. DDGS was first subjected to alkaline pretreatment with sodium hydroxide to remove the hemicellulose component and the generated carbohydrate-rich solids were then subjected to enzymatic hydrolysis using cellulase mixture Accellerase® 1500. When comparing separate hydrolysis and fermentation and simultaneous saccharification and fermentation (SSF) of L. coryniformis on DDGS hydrolysate, the latter method demonstrated higher d-lactic acid production (27.9 g/L, 99.9% optical purity of d-lactic acid), with a higher glucose to d-lactic acid conversion yield (84.5%) compared to the former one (24.1 g/L, 99.9% optical purity of d-lactic acid). In addition, the effect of increasing the DDGS concentration in the fermentation system was investigated via a fed-batch SSF approach, where it was shown that the d-lactic acid production increased to 38.1 g/L and the conversion yield decreased to 70%. In conclusion, the SSF approach proved to be an efficient strategy for the production of d-lactic acid from DDGS as it reduced the overall processing time and yielded high d-lactic acid concentrations.

Novel extremophilic proteases from Pseudomonas aeruginosa M211 and their application in the hydrolysis of dried distiller's grain with solubles

Proteases are the most important group of industrial enzymes and they can be used in several fields including biorefineries for the valorization of industrial byproducts. In this study, we purified and characterized novel extremophilic proteases produced by a Pseudomonas aeruginosa strain isolated from Mauritia flexuosa palm swamps soil samples in Peruvian Amazon. In addition, we tested their ability to hydrolyze distillers dried grains with solubles (DDGS) protein. Three alkaline and thermophilic serine proteases named EI, EII, and EIII with molecular weight of 35, 40, and 55 kDa, respectively, were purified. EI and EIII were strongly inhibited by EDTA and Pefabloc being classified as serine-metalloproteases, while EII was completely inhibited only by Pefabloc being classified as a serine protease. In addition, EI and EII exhibited highest enzymatic activity at pH 8, while EIII at pH 11 maintaining almost 100% of it at pH 12. All the enzymes demonstrated optimum activity at 60°C. Enzymatic activity of EI was strongly stimulated in presence of Mn²⁺ (6.9-fold), EII was stimulated by Mn²⁺ (3.7-fold), while EIII was slightly stimulated by Zn²⁺ , Ca²⁺ , and Mg²⁺ . DDGS protein hydrolysis using purified Pseudomonas aeruginosa M211 proteases demonstrated that, based on glycine released, EIII presented the highest proteolytic activity toward DDGS. This enzyme enabled the release 63% of the total glycine content in wheat DDGS protein, 2.2-fold higher that when using the commercial Pronase®. Overall, our results indicate that this novel extremopreoteases have a great potential to be applied in DDGS hydrolysis. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2728, 2019.

Biorefining of protein waste for production of sustainable fuels and chemicals

To mitigate the climate change caused by CO₂ emission, the global incentive to the low-carbon alternatives as replacement of fossil fuel-derived products continuously expands the need for renewable feedstock. There will be accompanied by the generation of enormous protein waste as a result. The economical viability of the biorefinery platform can be realized once the surplus protein waste is recycled in a circular economy scenario. In this context, the present review focuses on the current development of biotechnology with the emphasis on biotransformation and metabolic engineering to refine protein-derived amino acids for production of fuels and chemicals. Its scope starts with the explosion of potential feedstock sources rich in protein waste. The availability of techniques is applied for purification and hydrolysis of various feedstock proteins to amino acids. Useful lessons are leaned from the microbial catabolism of amino acids and lay a foundation for the development of the protein-based biotechnology. At last, the future perspective of the biorefinery scheme based on protein waste is discussed associated with remarks on possible solutions to overcome the technical bottlenecks.

Production of hydrophobic amino acids from biobased resources: wheat gluten and rubber seed proteins

Protein hydrolysis enables production of peptides and free amino acids that are suitable for usage in food and feed or can be used as precursors for bulk chemicals. Several essential amino acids for food and feed have hydrophobic side chains; this property may also be exploited for subsequent separation. Here, we present methods for selective production of hydrophobic amino acids from proteins. Selectivity can be achieved by selection of starting material, selection of hydrolysis conditions, and separation of achieved hydrolysate. Several protease combinations were applied for hydrolysis of rubber seed protein concentrate, wheat gluten, and bovine serum albumin (BSA). High degree of hydrolysis (>50 %) could be achieved. Hydrophobic selectivity was influenced by the combination of proteases and by the extent of hydrolysis. Combination of Pronase and Peptidase R showed the highest selectivity towards hydrophobic amino acids, roughly doubling the content of hydrophobic amino acids in the products compared to the original substrates. Hydrophobic selectivity of 0.6 mol-hydrophobic/mol-total free amino acids was observed after 6 h hydrolysis of wheat gluten and 24 h hydrolysis of rubber seed proteins and BSA. The results of experiments with rubber seed proteins and wheat gluten suggest that this process can be applied to agro-industrial residues.