Isolation and characterization of novel 1,3-propanediol-producing Lactobacillus panis PM1 from bioethanol thin stillage.

Conversion of glycerol to 1,3-propanediol (1,3-PDO) is an attractive option to increase the economic efficiency of the biofuel industry. A bacterial strain that produced 1,3-PDO in the presence of glycerol was isolated from thin stillage, the fermentation residue of bioethanol production. This 1,3-PDO-producing organism was identified as Lactobacillus panis through biochemical characteristics and by 16S rRNA sequencing. Characterization of the L. panis strain hereafter designated as PM1 revealed it was an aerotolerant acidophilic anaerobe able to grow over a wide range of temperatures; tolerant to high concentrations of sodium chloride, ethanol, acetic acid, and lactic acid; and resistant to many common antibiotics. L. panis PM1 could utilize glucose, lactose, galactose, maltose, xylose, and arabinose, but could not grow on sucrose or fructose. Production of 1,3-PDO by L. panis PM1 occurred only when glucose was available as the carbon source in the absence of oxygen. These metabolic characteristics strongly suggested NADH recycling for glucose metabolism is achieved through 1,3-PDO production by this strain. These characteristics classified L. panis PM1 within the group III heterofermentative lactic acid bacteria, which includes the well-characterized 1,3-PDO-producing strain, Lactobacillus reuteri. Metabolite production profiles showed that L. panis PM1 produced considerable amounts of succinic acid (~11-12 mM) from normal MRS medium, which distinguishes this strain from L. reuteri strains.

Composition and Properties of Aquafaba: Water Recovered from Commercially Canned Chickpeas.

Chickpea and other pulses are commonly sold as canned products packed in a thick solution or a brine. This solution has recently been shown to produce stable foams and emulsions, and can act as a thickener. Recently interest in this product has been enhanced through the internet where it is proposed that this solution, now called aquafaba by a growing community, can be used a replacement for egg and milk protein. As aquafaba is both new and being developed by an internet based community little is known of its composition or properties. Aquafaba was recovered from 10 commercial canned chickpea products and correlations among aquafaba composition, density, viscosity and foaming properties were investigated. Proton NMR was used to characterize aquafaba composition before and after ultrafiltration through membranes with different molecular weight cut offs (MWCOs of 3, 10, or 50 kDa). A protocol for electrophoresis, and peptide mass fingerprinting is also presented. Those methods provided valuable information regarding components responsible for aquafaba functional properties. This information will allow the development of practices to produce standard commercial aquafaba products and may help consumers select products of superior or consistent utility.

Production of Protein Concentrate and 1,3-Propanediol by Wheat-Based Thin Stillage Fermentation.

Fermentation of wheat with yeast produces thin stillage (W-TS) and distiller's wet grains. A subsequent fermentation of W-TS (two-stage fermentation, TSF) with endemic bacteria at 25 and 37 °C decreased glycerol and lactic acid concentrations, while 1,3-propanediol (1,3-PD) and acetic acid accumulated with greater 1,3-PD and acetic acid produced at 37 °C. During TSF, W-TS colloids coagulated and floated in the fermentation medium producing separable liquid and slurry fractions. The predominant endemic bacteria in W-TS were Lactobacillus panis, L. gallinarum, and L. helveticus, and this makeup did not change substantially as fermentation progressed. As nutrients were exhausted, floating particles precipitated. Protein contents of slurry and clarified liquid increased and decreased, respectively, as TSF progressed. The liquid was easily filtered through an ultrafiltration membrane. These results suggested that TSF is a novel method for W-TS clarification and production of protein concentrates and 1,3-PD from W-TS.

Conversion of Thin Stillage Compounds Using Endemic Bacteria Augmented with Lactobacillus panis PM1B.

A consortium of organisms, endemic in wheat-based thin stillage (W-TS), obtained from a commercial ethanol production converts glycerol to 1,3-propanediol (1,3-PD) and lactic acid to acetic acid. We sought to improve conditions for 1,3-PD and acetic acid production to be used in future studies of industrial isolation of these compounds from two-stage fermentation. Occasionally, stillage fermentation proceeded slowly, but an inoculum of Lactobacillus panis PM1B augmented both fermentation rate and extent. Fermentation rate and product yield were enhanced by adjusting pH to 5 daily and adding glucose and glycerol (molar ratio 0.1:1), freeze-dried W-TS, and vitamins (B2, B3, and B12). 1,3-PD and 3-hydroxypropionaldehyde (3-HPA) did not inhibit 1,3-PD production during fermentation. Moreover, agitation did not improve fermentation rate or extent. Corn sugar was a suitable substitute for glucose. Fermentation was performed at both 20 and 150 L with 1,3-PD production of 2% (w/v, 20 g/L) being routinely achieved or exceeded.

Protein Concentrate Production from Thin Stillage.

Two-stage fermentation (TSF) of saccharified wheat with a consortium of endemic lactobacilli produced CO2 and induced colloid separation of fermented solution to produce a protein concentrate (PC). Protein-rich slurry (50%, db) was obtained by decanting solution or skimming floating material during or after TSF. Washing and drying processes were explored to improve protein content, extend storage life of slurry, and yield converted stillage for compound recovery. Centrifuging and washing slurry afforded a PC and clarified solution. PC protein content increased to 60% (w/w, db). The PC was dried in a spray dryer or drum dryer or tray dryer. Dried PC water activity ranged 0.23-0.30. The dried PC lysine content was low, but lysine availability (95%) was excellent. Liquid from TSF and washing was readily microfiltered. Mass recovery of protein, glycerol, 1,3-propanediol, lactic acid, acetic acid, and glycerylphosphorylcholine from combined TSF, washing, and filtration were 66, 76, 72, 77, 74, and 84%, respectively.

Biorefinery process for protein extraction from oriental mustard (Brassica juncea (L.) Czern.) using ethanol stillage.

Large volumes of treated process water are required for protein extraction. Evaporation of this water contributes greatly to the energy consumed in enriching protein products. Thin stillage remaining from ethanol production is available in large volumes and may be suitable for extracting protein rich materials. In this work protein was extracted from ground defatted oriental mustard (Brassica juncea (L.) Czern.) meal using thin stillage. Protein extraction efficiency was studied at pHs between 7.6 and 10.4 and salt concentrations between 3.4 × 10-2 and 1.2 M. The optimum extraction efficiency was pH 10.0 and 1.0 M NaCl. Napin and cruciferin were the most prevalent proteins in the isolate. The isolate exhibited high in vitro digestibility (74.9 ± 0.80%) and lysine content (5.2 ± 0.2 g/100 g of protein). No differences in the efficiency of extraction, SDS-PAGE profile, digestibility, lysine availability, or amino acid composition were observed between protein extracted with thin stillage and that extracted with NaCl solution. The use of thin stillage, in lieu of water, for protein extraction would decrease the energy requirements and waste disposal costs of the protein isolation and biofuel production processes.

Rapid NMR method for the quantification of organic compounds in thin stillage.

Thin stillage contains organic and inorganic compounds, some of which may be valuable fermentation coproducts. This study describes a thorough analysis of the major solutes present in thin stillage as revealed by NMR and HPLC. The concentration of charged and neutral organic compounds in thin stillage was determined by excitation sculpting NMR methods (double pulse field gradient spin echo). Compounds identified by NMR included isopropanol, ethanol, lactic acid, 1,3-propanediol, acetic acid, succinic acid, glycerophosphorylcholine, betaine, glycerol, and 2-phenylethanol. The concentrations of lactic and acetic acid determined with NMR were comparable to those determined using HPLC. HPLC and NMR were complementary, as more compounds were identified using both methods. NMR analysis revealed that stillage contained the nitrogenous organic compounds betaine and glycerophosphorylcholine, which contributed as much as 24% of the nitrogen present in the stillage. These compounds were not observed by HPLC analysis.