Biology subjects

Mockaitis, G.

Publications and source records attributed to Mockaitis, G..

8 recordsLinked to original sources

bioRxiv2023

Mixotrophic microalgal mixed cultures for cheese whey valorization

Microalgae cultivation, and phycoremediation, can be a polishing step in wastewater treatment. Depending on the stream utilized for microalgal cultivation, biomass can be contaminated with considerable quantities of heavy metals and xenobiotics. Given the economic value of microalgae bioproducts, we suggest coupling anaerobic fermentation with microalgae mixotrophic growth. Cheese whey, a product from cheese production, has a 2022 forecast production of 160.7 million m3 year-1 in which about 66.5 million m3 y-1 is used as animal feed, fertilizers or illegally discharged causing eutrophication. Anaerobic fermentation of cheese whey produces volatile fatty acids (VFAs) such as acetate which serves as an organic carbon source for photoorganoheterotrophic microalgal biomass growth. Our work selected three organic sources derived from cheese whey: 40% demineralized whey powder (WPC40), lactose, and acetate. In photolitoautotrophic conditions, green phototrophic growth was successful. In batch tests, acetate was the best organic carbon source among photoorganoheterotrophs with a higher yield of 1.15 mg VSS mg Carbon-1 (C) in anaerobic conditions. Also, acetate uptake was thought to be via the glyoxylate cycle. When upscaling the experiment in a chemostat, a lower dilution rate of 0.17 d-1 was more suitable for green photoorganoheterotrophs selection, as they were not washed out in the process. These findings show that acetate uptake by microalgae in mixotrophic regimes must be better understood as well as reinforce the advantages of coupling microalgal biomass growth with cheese whey acidogenic fermentation, avoiding contaminations as in phycoremediation processes and fully valorizing cheese whey. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/563819v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@16658c0org.highwire.dtl.DTLVardef@4ce591org.highwire.dtl.DTLVardef@73b8b2org.highwire.dtl.DTLVardef@162eef9_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2023

Thermal and alkaline pre-treatments of inoculum halt methanogenesis and enables cheese whey valorization by batch acidogenic fermentation

Carboxylates like volatile fatty acids (VFAs) can be produced by acidogenic fermentation (AF) of dairy wastes like cheese whey, a massive residue produced at 160.67 million m3 of which 42% are not valorized and impact the environment. In mixed-culture fermentations, selection pressures are needed to favor AF and halt methanogenesis. Inoculum pre-treatment was studied here as selective pressure for AF demineralized cheese whey in batch processes. Alkaline (NaOH, pH 8.0, 6 h) and thermal (90{degrees}C for 5 min, ice-bath until 23{degrees}C) pre-treatments, were tested together with batch operations run at initial pH 7.0 and 9.0, food-to-microorganism (F/M) ratios of 0.5 to 4.0 g COD g-1 VS, and under pressurized and non-pressurized headspace, in experiments duplicated in two institutes. Acetic acid was highly produced (1.36 and 1.40 g CODAcOH L-1) at the expense of methanogenesis by combining a thermal pre-treatment of inoculum with a non-pressurized batch operation started at pH 9.0. Microbial communities comprised of VFAs and alcohol producers, such as Clostridium, Fonticella, and Intestinimonas, and fermenters such as Longilinea and Leptolinea. Communities also presented the lipid-accumulating and bulk and foaming Candidatus Microthrix and the metanogenic Methanosaeta regardless of no methane production. An F/M ratio of 0.5 g COD g-1 VS led to the best VFA production of 1,769.38 mg L-1. Overall, inoculum thermal pre-treatment, initial pH 9.0, and non-pressurized headspace acted as a selective pressure for halting methanogen and producing VFAs, valorizing cheese whey via batch acidogenic fermentation.

bioengineering↗

bioRxiv2022

Use of Fe3O4 nanoparticles in reactor co-digestion of residues from 1G2G ethanol biorefinery: microbiological routes and operational aspects

The co-digestion of residues from the sugarcane industry has already proven to be a highly attractive process for biogas production through anaerobic digestion (AD). The use of residues such as vinasse (1G) filter cake (1G) and deacetylation liquor (2G) in CSTR operation showed the potential for integrating 1G and 2G ethanol biorefineries through AD in previous work by our research group. The use of nanoparticles (NP) is a favorable way to optimize AD processes, as these additives allow the introduction of nutrients to the process more assertively concerning the distribution and interaction with microorganisms. The present work proposed the optimization of the co-digestion of vinasse, filter cake, and deacetylation liquor in a continuous reactor by adding Fe3O4 NP, comparing the results with a previous reactor operation without NP. Initially, tests were carried out in batches with different NP concentrations, resulting in 5 mg L-1 as the best concentration to be added in the continuous reactor along the increments of the applied organic rate load (ORL). CH4 production reached a maximum value of 2.8 {+/-} 0.1 NLCH4 gVS-1 and the organic matter removal reached 71 {+/-} 0.9%, in phase VI (ORL of 5.5 gVS L-1 day-1). This production was 90% higher than the reactor co-digestion operation without NP. The pH and alkalinity results indicated the methanogenesis stabilization within 60 days of operation: 30 days before when there was no NP added. The AD development was stable, presenting low variations in the oxidation-reduction potential (ORP) and stable organic acid (OA) concentrations, which indicated the propionic acid route to produce CH4 was predominant. The main methanogenic Archeae identified was Methanoculleus, indicating that the predominant metabolic route was that of acetate (SAO) coupled with hydrogenotrophic methanogenesis. The use of Fe3O4 NP managed to improve the AD from the 1G2G ethanol production residues and stimulated the microbial community growth, not modifying the preferable metabolic pathways.

bioengineering↗

bioRxiv2021

Effect of Inoculum Pretreatment on Alcohol Production from Volatile Fatty Acids through an Anaerobic Solventogenic Process

1This work evaluates four different physicochemical pretreatments (acidic, thermal, acidic-thermal and thermal-acidic) on an anaerobic inoculum used for alcohol production from acetate and butyrate. All experiments were conducted in single batches using acetate and butyrate as substrates at 30 {degrees}C and with a pressurized headspace of pure H2 at 2.15 atm (218.2 MPa). Thermal and acidic-thermal pretreatments lead to higher production of both ethanol and butanol. Mathematical modelling shows that the highest attainable concentrations of ethanol and butanol produced were 122 mg L-1 and 97 mg L-1 for the thermal pretreatment (after 17.5 days) and 87 mg L-1 and 143 mg L-1 for the acidic-thermal pretreatment (after 18.9 days). Acetate was produced in all assays. Thermodynamic data indicated that a high H2 partial pressure favoured solventogenic metabolic pathways. Finally, sequencing data showed that both thermal and acidic-thermal pretreatments selected mainly the bacterial genera Pseudomonas, Brevundimonas and Clostridium. The acidic-thermal pretreatment selected a bacterial community more adapted to the conversion of acetate and butyrate into ethanol and butanol, respectively. Thermal-acidic pretreatment was unstable, showing significant variability between replicates. Acidic pretreatment showed the lowest alcohol production.

bioengineering↗

bioRxiv2021

Effect of Initial pH and Organic Matter Concentration on Production of Volatile Organic Acids Through Acidogenesis of Sugarcane Vinasse

Sugarcane vinasse is an industrial liquid waste generated in great amounts in Brazilian ethanol industries. Nowadays its main use occurs at sugarcane crops, where vinasse is applied as a nutrient source for fertirrigation. However, continued use of vinasse in soil can cause several environmental impacts. So, aiming to provide a more environmentally friendly destination to the effluent, the goal of this work was to investigate the acidogenesis using a synthetic vinasse as substrate, focusing on the effects of initial pH and Chemical Oxygen Demand (COD) on short chain organic acids (SCOAs) concentrations. Synthetic vinasse was prepared at laboratory taking some real sugarcane vinasse composition given in previous works as references. So, major contribution presented here is the investigation on obtaining high added-value SCOAs from a simulated effluent. Cattle manure sludge was utilized as inoculum to promote the conversion of carbohydrate (sucrose, Suc) in synthetic vinasse into SCOAs in batch reactors during a total incubation time of 72 h. Acidogenesis profiles have shown that concentration of lactic acid (HLa) was prevailing among all metabolites, indicating that process followed through an essentially lactic route. Furthermore, considerable concentrations of propionic, acetic and isobutyric acids were also verified at some specific operation times, while solventogenesis was not detected at all. The greatest peak of lactate content was 4.96 g HLa L-1, observed under initial pH 6.0 and 25 g COD L-1, at 16 h. Maximum of lactate productivity was 332.10 g HLa L-1 h-1 at 8 h, associated to a yield of 189.14 g HLa (g Suc)-1, under initial pH 7.5 and 20 g COD L-1.

bioengineering↗

bioRxiv2021

Acidogenic Fermentation of Sugarcane Vinasse and Glucose Using Two Different Anaerobic Digestion Inocula

Vinasse is an agroindustrial wastewater obtained at large amounts in countries such as Brazil, which is one of the world greatest sugar and ethanol producers from sugarcane. Despite its most common use is as nutrient for fertirrigation in sugarcane crops nowadays, alternative processing has been intensely sought in last decades for vinasse aiming primarily the production of energy carriers and high-added value chemicals. One of these alternatives is the anaerobic digestion promoted by bacteria, which results in several products of economic importance. In view of these information, this work presents an investigation of acidogenic fermentation by C. acetobutylicum ATCC 824 and C. beijerinckii ATCC 25752 was conducted in batch reactors by using synthetic vinasse and aqueous glucose solution as substrates. Evaluation of effects of microorganism and carbon source was focused mainly on the production of short chain organic acids (SCOAs), although other metabolites, such as ethanol, were also detected. Carbohydrates were effectively consumed by bacteria, so remaining concentrations of sucrose and glucose (Suc and Glu) in both substrates were considerably low at the end of tests. Lactic acid (HLa) was the prevailing metabolite in all experiments, determining the trends observed for total SCOAs content as a function of incubation time, while other acids were generated in much lesser amounts. Moreover, ethanol (EtOH) attained notably higher concentrations in batch reactors containing glucose as substrate, which showed more relevant production of this chemical. Maximum of 14.1 g HLa L-1 was quantified for lactic acid at incubation time 96 h in reactor using synthetic vinasse and C. beijerinckii (VB), linked to a productivity P = 146.46 mg HLa L-1 h-1 and a yield Y = 1108.03 mg HLa (g Sue)-1. For ethanol, maximum was 1.6 g EtOH L-1, occurring in reactor containing glucose and C. acetobutylicum (GA) also at incubation time 90 h, resulting in P = 13.60 mg EtOH L-1 h-1 and Y = 73.04 mg EtOH (g Glu)-1. Finally, kinetic models were adjusted to experimental data of carbohydrate content, lactate concentration and optical density (indicative of microorganism growth), showing good prediction capability as suggested by values of fit quality parameters such as Residual Sum of Squares (RSS) and R2.

bioengineering↗

bioRxiv2021

Lactic Acid Production by Clostridium acetobutylicum and Clostridium beijerinckii Under Anaerobic Conditions Using a Complex Substrate

SUMMARY/ ABSTRACTHigh societies consumption, elevated residues generation and environmental awareness strengthen alternatives solutions for bioprocess residues. This study investigated the production of volatile acids from a complex substrate, which intends to be replaceable in the future by vinasse of sugar cane, in anaerobic reactors operated in triplicates at 35 {degrees}C. Two different inoculum were studied: Clostridium acetobutylicum ATCC 824 and Clostridium beijerinckii ATCC 25752. The nutrient medium had as carbon source a complex substrate containing sucrose without addition of vitamins, buffer solution and micronutrients. The experiment was conducted in the variation of F/M-ratio (food-to-microorganisms) by increasing substrate concentration. The concentration of sucrose in the complex substrate were 5.2 g{middle dot}L-1 (conditions of 10,000 mg O2{middle dot} L-1 in terms of COD) and 10.5 g{middle dot} L-1 (conditions of 20,000 mg O2{middle dot}L-1 in terms of COD), keeping the initial concentration of inoculum in 500 mg SVT{middle dot}L-1. Cultures C. acetobutylicum and C. beijerinckii resulted in high lactic acid production. Concentrations of COD of 10,000 mg O2{middle dot} L-1 produced optimum lactic acid of 3,331 mg{middle dot}L-1 and 5,709 mg{middle dot}L-1 with respectively C. acetobutylicum and C. beijerinckii. Moreover, cultures C. acetobutylicum and C. beijerinckii with 20,000 mg O2{middle dot} L-1 concentrations in terms of COD produced optimum lactic acid of 6,417 mg{middle dot} L-1 and 7.136 mg{middle dot}L-1 respectively. There was repeatability in the reactors when considering level of significance of 0.05, independent of the concentration and inoculum used.

bioengineering↗

bioRxiv2021

Biochemical Methane Potential (BMP) from sugarcane biorefinery residues: maximizing their use by co-digestion

This is a pioneer study evaluating the methane (CH4) production potential from residues of integrated 1st (vinasse and filter cake) and 2nd (deacetylation pretreatment liquor from straw) generation (1G2G) sugarcane biorefinery, providing a fully chemical characterization of them and their relation with the anaerobic digestion (AD) process. Small-scale assays provided fundamentals for basing the co-digestion optimization by assessing the optimal co-substrates synergistic conditions. Biochemical Methane Potential (BMP) tests showed co-digestion enhanced CH4 yield of isolated substrates, reaching up to 605 NmLCH4 gVS-1. The association of vinasse and deacetylation liquor as co-substrates increased the BMP by ~38% mostly by nutritionally benefiting the methanogenic activity. The kinetic analysis confirmed that the deacetylation liquor was the co-substrate responsible for improving the CH4 production in the co-digestion systems due to the highest CH4 conversion rate. The alkaline characteristic of the liquor (pH~12) also prevented alkalizing from being added to the co-digestion, an input that normally makes the process economically unfeasible to implement on an industrial scale due to the large quantities required for buffering the reactor. The filter cake had the lowest BMP (262 NmLCH4 gVS-1) and digestibility ([≤] 40%), further limited by the required stirring to improve the mass transfer of biochemical reactions. The present study drives towards more sustainable use of vinasse, the most voluminous waste from the sugarcane industry, and lignin-rich residues derived from pre-treatment alkaline methods, aiming at an energy-efficient utilization, by at least 16% when compared to the traditional vinasse AD. The experimental and modeling elements from this work indicated the lignin-rich liquor is the main responsible for putting the co-digestion as a disruptive technological arrangement within the 1G2G sugarcane biorefineries, reinforcing the biogas production as the hub of the bioeconomy in the agroindustrial sector.

bioengineering↗