Volatile fatty acid platform - a cornerstone for the circular bioeconomy.

Annually, the EU produces more than 100 million tonnes of urban biowaste, which is largely under-valorized and in some cases even still landfilled without any energy or material recovery. If Europe wants to be ready for the future, it will need to make better use of this large biomass potential within a circular economy approach. The research project funded by the European Commission under the Horizon 2020 programme entitled 'VOLATILE-Biowaste derived volatile fatty acid platform for biopolymers, bioactive compounds and chemical building blocks' aimed to produce volatile fatty acids (VFAs) from biowaste for reprocessing into products, materials or substances to close the material loop. During the project, the partners were able to obtain average volatile fatty acid yields of 627 g COD/kg organic matter (OM) for food waste, 448 g COD/kg OM for separately collected vegetable, garden and fruit waste (VGF) and 384 g COD/kg OM for the organic fraction of municipal solid waste (OF-MSW) at concentrations ranging from 12 to 48 g/L, 6 to 40 g/L and 13 to 26 g/L, respectively. A membrane filtration cascade consisting of micro-, ultra- and nano-filtration followed by reverse osmosis was identified as a feasible way to purify and concentrate the VFA effluent, making them a suitable carbon source for further fermentation processes. Besides technical optimization, socio-economic and legal aspects associated with this platform technology were also studied and show that although this technology is still in development, it is providing an answer to changing societal and market expectations both regarding organic waste treatment and bio-based production strategies. Based on the current technological, economic and market evolutions, it is expected that the VFAP will play an important role in organic waste treatment in the coming years.

VOLATILE FATTY ACIDS FROM ORGANIC WASTES AS NOVEL LOW-COST CARBON SOURCE FOR Yarrowia lipolytica.

Microbial oil biosynthesis is envisaged as a promising technology for sustainable production of chemicals and fuels. Sugar-based substrates are the most typical carbon sources used for this purpose where metabolic pathways and stoichiometry are well known. However, the use of low-cost substrates is crucial for the economic viability of the process. Volatile fatty acids (VFAs) are considered to be a novel low-cost carbon source for microbial lipid production. They can be utilized by oleaginous yeasts to produce and store fatty acids in form of intracellular lipid bodies. In this work, Yarrowia lipolytica growth and substrate consumption were evaluated using the major VFAs present in anaerobic effluents. Individual VFAs as well as synthetic mixtures were tested at different concentrations to determine uptake rates and potential toxicity. Increasing VFA chain length resulted in greater biomass yield although, when added individually, 4 g Carbon/L VFA (e.g. 6.45 g/L of caproic and 10 g/L of acetic acid) caused inhibitory effects. Remarkably, biomass growth increased by 2.5-fold on real anaerobic fermentation effluent compared with synthetic mixtures. When real digestate was supplemented with synthetic VFAs up to 26.5 g/L, the inhibitory effect of the acids was counterbalanced. The results provided evidence of robustness of Y. lipolytica towards low-cost fermentation effluents and present this yeast as a promising candidate for the sustainable production of microbial oil using real digestates.

Microbial Production of Short Chain Fatty Acids from Lignocellulosic Biomass: Current Processes and Market.

Biological production of organic acids from conversion of biomass derivatives has received increased attention among scientists and engineers and in business because of the attractive properties such as renewability, sustainability, degradability, and versatility. The aim of the present review is to summarize recent research and development of short chain fatty acids production by anaerobic fermentation of nonfood biomass and to evaluate the status and outlook for a sustainable industrial production of such biochemicals. Volatile fatty acids (VFAs) such as acetic acid, propionic acid, and butyric acid have many industrial applications and are currently of global economic interest. The focus is mainly on the utilization of pretreated lignocellulosic plant biomass as substrate (the carbohydrate route) and development of the bacteria and processes that lead to a high and economically feasible production of VFA. The current and developing market for VFA is analyzed focusing on production, prices, and forecasts along with a presentation of the biotechnology companies operating in the market for sustainable biochemicals. Finally, perspectives on taking sustainable product of biochemicals from promise to market introduction are reviewed.

Effects of pH control and concentration on microbial oil production from Chlorella vulgaris cultivated in the effluent of a low-cost organic waste fermentation system producing volatile fatty acids.

The objective of this study was to investigate the feasibility of applying volatile fatty acids (VFAs) produced from low-cost organic waste to the major carbon sources of microalgae cultivation for highly efficient biofuel production. An integrated process that consists of a sewage sludge fermentation system producing VFAs (SSFV) and mixotrophic cultivation of Chlorella vulgaris (C. vulgaris) was operated to produce microbial lipids economically. The effluents from the SSFV diluted to different concentrations at the level of 100%, 50%, and 15% were prepared for the C. vulgaris cultivation and the highest biomass productivity (433±11.9 mg/L/d) was achieved in the 100% culture controlling pH at 7.0. The harvested biomass included lipid contents ranging from 12.87% to 20.01% under the three different effluent concentrations with and without pH control. The composition of fatty acids from C. vulgaris grown on the effluents from the SSFV complied with the requirements of high-quality biodiesel. These results demonstrated that VFAs produced from the SSFV are favorable carbon sources for cultivating C. vulgaris.

Economic process to produce biohydrogen and volatile fatty acids by a mixed culture using vinasse from sugarcane ethanol industry as nutrient source.

This work evaluates the potential of vinasse (a waste obtained at the bottom of sugarcane ethanol distillation columns) as nutrient source for biohydrogen and volatile fatty acids production by means of anaerobic consortia. Two different media were proposed, using sugarcane juice or molasses as carbon source. The consortium LPBAH1 was selected for fermentation of vinasse supplemented with sugarcane juice, resulting in a higher H2 yield of 7.14 molH2 molsucrose(-1) and hydrogen content in biogas of approx. 31%, while consortium LPBAH2 resulted in 3.66 molH2/molsucrose and 32.7% hydrogen content in biogas. The proposed process showed a rational and economical use for vinasse, a mandatory byproduct of the renewable Brazilian energy matrix.

Short-chain fatty acid enemas: a cost-effective alternative in the treatment of nonspecific proctosigmoiditis.

The purpose of this study was to perform a randomized, prospective comparison of corticosteroid enemas (CS--100 mg of hydrocortisone/60 cc P.R. q.h.s.; n = 12), mesalamine enemas (5-ASA--4 g/60 cc P.R. q.h.s.; n = 19), and short-chain fatty acid enemas (SCFA--60 cc P.R. b.i.d.; n = 14) for the treatment of proctosigmoiditis. Patients presenting to the Ferguson Clinic with the diagnosis of idiopathic proctosigmoiditis were evaluated for age, sex, prior history of proctitis, duration of symptoms prior to presentation, endoscopic scoring, and mucosal biopsies. Clinical evaluation was performed at two-week intervals for six weeks, with repeat biopsies taken at six weeks. There was no significant difference with respect to age, male/female ratio, past history of proctosigmoiditis, length of colorectum involved at the time of initial presentation, symptom resolution, and endoscopic and histologic improvement among the three treatment groups. Recovery occurred in a similar proportion in each of the three groups: CS, 10/12; 5-ASA, 17/19; and SCFA, 12/14. The cost of six weeks of treatment was: CS, $71.82; 5-ASA, $347.28; and SCFA, $31.50. This study indicates that SCFA enemas are equally efficacious to CS or 5-ASA enemas for the treatment of proctosigmoiditis at a significant cost savings.