Recycled Medium Research Articles

A sustainable bioprocessing system leveraging gas fermentation and bipolar membrane electrodialysis system for direct recovery of acetic acid

This study examined the integration of gas fermentation with bipolar membrane electrodialysis (BPMED) for sustainable production of acetic acid and bases, focusing on medium recycling and ion-exchange membrane optimisation. Gas fermentation was performed using an acetogenic microbe, Eubacterium callanderi KIST612, in a custom-designed gas bioreactor. The BPMED system was operated under specific voltage conditions to evaluate the proton and hydroxyl ion generation, ion concentration, and residual ratios. Gas fermentation consistently generated acetate with a stable CO2 consumption rate (0.167 mmol gcell−1) and an increased rate of conversion of carbon into biochemicals via methanol. The BPMED system efficiently produced acetic acid (acetate extraction rate of 99.72 %–99.82 %) and hydroxide ions (from 8 to 18 V), with operational challenges identified at higher voltage levels (≥20 V). The BPMED process, which includes additional membranes and exhibits a lower acetate flux than the ED process, had remarkable cost-effectiveness, surpassing the ED integration process by 17.6 %. This economic advantage was paralleled by a significant environmental benefit, where the BPMED process reduced carbon dioxide emissions by 7.4 % compared with the ED process. These results suggest that integrating gas fermentation with BPMED is a viable and sustainable approach for acetic acid production.

Recycling of nutrient medium to improve productivity in large-scale microalgal culture using a hybrid electrochemical water treatment system

Recycling and reusing of nutrient media in microalgal cultivation are important strategies to reduce water consumption and nutrient costs. However, these approaches have limitations, e.g., a decrease in biomass production, (because as reused media can inhibit biomass growth). To address these limitations, we applied a novel membrane filtration‒electrolysis‒ultraviolet hybrid water treatment method capable of laboratory-to-large-scale operation to increase biomass productivity and enable nutrient medium disinfection and recycling. In laboratory-scale experiments, electrolysis effectively remove the biological contaminants from the spent nutrient medium, resulting in a high on-site removal efficiency of dissolved organic carbon (DOC; 80.3 ± 5 %) and disinfection (99.5 ± 0.2 %). Compared to the results for the recycling of nutrient medium without water treatment, electrolysis resulted in a 1.5-fold increase in biomass production, which was attributable to the removal of biological inhibitors from electrochemically produced oxidants (mainly OCl−). In scaled-up applications, the hybrid system improved the quality of the recycled nutrient medium, with 85 ± 2 % turbidity removal, 75 ± 3 % DOC removal, and 99.5 ± 2 % disinfection efficiency, which was beneficial for biomass growth by removing biological inhibitors. After applying the hybrid water treatment method, we achieved a Spirulina biomass production of 0.47 ± 0.03 g L−1, similar to that obtained using a fresh medium (0.53 ± 0.02 g L−1). The on-site disinfection process described herein is practical and offers a cost-saving and environmental friendly alternative for nutrient medium recycling and reusing water in mass and sustainable cultivation of microalgae.

Comprehensive understanding of the regulatory mechanism by which selenium nanoparticles boost CO2 fixation and cadmium tolerance in lipid-producing green algae under recycled medium

Recycled medium plus cadmium is a promising technique for reducing the cultivation cost and enhancing the yield of microalgae lipids. However, oxidative stress and cadmium toxicity significantly hinder the resulting photosynthetic efficiency, cell growth and cell activity. Herein, selenium nanoparticles (SeNPs) were used to increase the total biomass, biolipid productivity, and tolerance to cadmium. Wide-ranging analyses of photosynthesis, energy yield, fatty acid profiles, cellular ultrastructure, and oxidative stress biomarkers were conducted to examine the function of SeNPs in CO2 fixation and cadmium resistance in Ankistrodesmus sp. EHY. The application of 15 μM cadmium and 2 mg L−1 SeNPs further enhanced the algal biomass productivity and lipid productivity to 500.64 mg L−1 d−1 and 301.14 mg L−1 d−1, respectively. Moreover, the rates of CO2 fixation, chlorophyll synthesis and total nitrogen removal were similarly increased by the application of SeNPs. Exogenous SeNPs strengthened cell growth and cadmium tolerance by upregulating photosynthesis, the TCA cycle and the antioxidant system, reducing the uptake and translocation of cadmium, and decreasing the levels of reactive oxidative stress (ROS), extracellular polymeric substances (EPSs) and cellular Cd2+ level in EHY under recycled medium and cadmium stress conditions. Additionally, a maximum energy yield of 127.40 KJ L−1 and a lipid content of 60.15% were achieved in the presence of both SeNPs and cadmium stress. This study may inspire the efficient disposal of recycled medium and biolipid production while also filling the knowledge gaps regarding the mechanisms of SeNP functions in carbon fixation and cadmium tolerance in microalgae.

Upstream bioprocessing of Spirulina platensis microalgae using rainwater and recycle medium from post-cultivation for C-phycocyanin production

BackgroundThe cultivation of microalgae represents a water-intensive process, prompting the need to reduce its water footprint and explore alternative water sources. Therefore, this research work aims to investigate the growth of Spirulina by recycling the culture medium obtained from the post-cultivation process and substituting rainwater resources for the preparation of the culture medium. MethodsThe effect of pre-treatment methods, specifically microfiltration and UV-light was investigated. These methods were applied to treat the recycled medium and rainwater resources used for Spirulina cultivation. Biomass concentration, biomass productivity and phycocyanin accumulation of Spirulina were examined to assess the Spirulina growth under different pre-treatment conditions. Significant FindingsAfter three cultivation cycles in the recycled medium, biomass productivity decreased from 0.2246 to 0.0802 g/L/d which might be due to high salinity and biological pollutants that inhibit Spirulina growth. However, different pre-treatment methods using microfiltration and UV-light on the recycling medium were found to be effective in increasing biomass productivity from 0.1395 to 0.1861 g/L/d. Additionally, the use of rainwater for Spirulina cultivation was explored. Applying pre-treatment methods to the rainwater, biomass productivity was further improved from 0.3211 to 0.3837 g/L/d. These findings suggest that the use of pre-treatment methods and alternative rainwater resources can improve the biomass productivity of Spirulina and potentially reduce the environmental impact throughout the microalgae cultivation process.

Optimizing fucoxanthin production from Phaeodactylum tricornutum: Impact of harvesting methods on culture medium reusability

The growing demand for naturally-synthesized fucoxanthin has driven increased focus on microalgae-based production methods. However, the high costs associated with microalgae harvesting and processing remain a significant challenge. To overcome this obstacle and promote the development of the microalgae-based fucoxanthin industry, this study aimed to develop an efficient and cost-effective methods for harvesting Phaeodactylum tricornutum, a promising microalgal strain for fucoxanthin production, while maximizing the reuse of the culture medium. This study investigated the feasibility of reusing the FeCl3-based flocculation medium for P. tricornutum cultivation, and explored the optimal proportion of recycled supernatant and fresh medium for maximizing biomass and fucoxanthin yield of P. tricornutum. It also examined the effect of residual iron on harvested biomass and pigment and proposed a simple washing method for its removal. The results showed that FeCl3-based flocculation was highly effective (>93 %) in harvesting P. tricornutum, and a 50/50 proportion of recycled medium and fresh medium can be used without significant negative effects on biomass and fucoxanthin productivity, allowing a reduction of approximately 43 % water consumption. Although a negative effect on algal fucoxanthin content was observed, the productivity of fucoxanthin per unit volume (mg/L) did not decrease compared to centrifugation-based algae cells. Furthermore, simple washing with water can effectively remove the residual iron from the harvested biomass or pigment, resulting in a reduction of approximately 42 % and 64 %, respectively. These findings suggest that the reuse of FeCl3-based flocculation medium for P. tricornutum cultivation is feasible and holds promise for cost-effective fucoxanthin production. This study contributes to develop a sustainable approach for microalgae-based fucoxanthin production at a lower cost and higher production capacity, benefiting both society and industry.

Artificial intelligence model for monitoring biomass growth in semi-batch Chlorella vulgaris cultivation

There is a great demand for a clean, economical, and long-term energy source, due to the depletion of fossil fuels. Large-scale production of microalgae biomass for biofuel production is likely attributable to several challenges, including the high cost of photobioreactors, the need for a sustainable medium for optimum development, and time-consuming algal growth monitoring techniques. Firstly, the research novelty aims at improving the strategy of recycling culture media for semi-batch cultivation of Chlorella vulgaris. Two cycles were performed with varying amounts of recycled medium replacement to evaluate algal growth and biochemical content. As compared to all other culture ratio combinations, the mixing ratio of recycled medium to fresh medium is at 40 % (40RB) combination yielded the greatest biomass growth (4.52 g/L), lipid (317.40 mg/g), protein (280.57 mg/g), and carbohydrate (451.37 mg/g) content. Next, custom vision was applied to Chlorella vulgaris maturing stages, and a unique digital architecture framework was developed. The iteration model delivers result interpretation with an accuracy of more than 92 % of every data set based on the trained Model Performance.

Process Development of Polyhydroxyalkanoates Production by Halophiles Valorising Food Waste.

Polyhydroxyalkanoates (PHA) is an emerging biodegradable plastic family that can replace a broad spectrum of conventional thermoplastics and is promising in the sustainable process development and valorization of organic waste. This study established a novel production system of PHA from food waste through halophilic microbial fermentation with spent medium recycling. The essential processing parameters for batch cultivation of Haloferax mediterranei were optimized for food waste substrate (a 40 g/L loading and 2.5 vvm of aeration), which achieved a yield of 0.3 g PHA/g COD consumed. A batch bioreactor system was developed, which produced 7.0 ± 0.7 g/L cell dry mass and 4.5 ± 0.2 g/L PHA with a 20% dissolved oxygen (DO) level. A DO above 50% saturation resulted in faster cell growth and similar cell mass production but 25% less PHA production. The spent saline medium, treated with H2O2 and rotary evaporation, was successfully reused for four consecutive batches and provided consistent PHA concentrations and product qualities.

A low-cost technique for biodiesel production in Ankistrodesmus sp. EHY by using harvested microalgal effluent

The present study aims to use Ankistrodesmus sp. EHY to develop a viable and economic lipid production strategy using recycling of harvested microalgal effluent. In comparison to the control, the highest lipid content (52.4 %) and productivity (250.72 mg L−1 d−1) were achieved when 40 % recycled medium was used. Consistent with the trend of lipid accumulation, the six key lipogenetic genes were upregulated, as well as reactive oxygen species (ROS), glutathione (GSH) and genes encoding antioxidant enzymes during cultivation in recycled medium. Moreover, the consumption of dissolved organic carbon (DOC) and the increased humic acid (HA) in the recycled medium might also be associated with lipid biosynthesis. The biodiesel parameters of alga biomass-derived lipids were fitted to the standard of commercial biodiesel. In conclusion, this study offers an economically viable strategy for microalgal biofuel production and wastewater treatment using recycling of harvested microalgal effluent.

Photocatalytic oxidation degradation of inhibitory fatty acids for aged Chlorella vulgaris cultivation medium recycling.

The medium used for Chlorella vulgaris cultivation exerted obvious inhibitory effects on the growth of C. vulgaris after several culture-harvest cycles. The accumulated fatty acids secreted by C. vulgaris during their growth process were expected to be the cell inhibition components. In this work, the ultraviolet-driven photocatalytic oxidation technique was applied for the degradation of microalgae cell growth inhibition components in the aged cultivation medium, and the reaction parameters were optimized. The results indicated that the photocatalytic oxidation processes using 0.5g/L [Formula: see text] NPs as the catalyst under the aeration condition showed as high as 74.61 ± 4.60% FA degradation efficiency after 20min illumination, and the contents of -COOH, [Formula: see text] (α) and -COO-R functional groups in the aged C. vulgaris medium were significantly reduced. In addition, the modification of the photocatalyst further improved the ability of the degradation of FA. When the modified [Formula: see text]/AC and [Formula: see text]/Ag catalysts were applied, the FA degradation rates reached as high as 92.46 ± 0.37% and 93.91 ± 1.37%, respectively. In the recycled medium treated with [Formula: see text]/AC, the cell density in the stable phase reached 96.33 ± 1.83% of that in the fresh medium as the control. In summary, the photocatalytic oxidation with the modified [Formula: see text]/AC catalyst was proposed as the efficient strategy to realize the recycling of the aged C. vulgaris cultivation medium via the degradation of the FA as the cell growth inhibitors.

Treatment of secondary urban wastewater with a low ammonium-tolerant marine microalga using zeolite-based adsorption

The low tolerance of marine microalgae to ammonium and hyposalinity limits their use in urban wastewater (UWW) treatments. In this study, using the marine microalga Amphidinium carterae, it is demonstrated for the first time that this obstacle can be overcome by introducing a zeolite-based adsorption step to obtain a tolerable UWW stream. The maximum ammonium adsorption capacities measured in the natural zeolite used are among the highest reported. The microalga grows satisfactorily in mixtures of zeolite-treated UWW and seawater at a wide range of proportions, both with and without adjusting the salinity, as long as the ammonium concentration is below the threshold tolerated by the microalgae (6.3 mg L−1). A proof of concept performed in 10-L bubble column photobioreactors with different culture strategies, including medium recycling, showed an enhanced biomass yield relative to a control with no UWW. No noticeable effect was observed on the production of specialty metabolites.

Nanoconfinement Effects of Micellar Media in Asymmetric Catalysis

AbstractReplacement of organic solvents, in particular chlorinated, aromatic, and polar aprotic ones, is an emerging issue that can find a solution in the development of catalytic reactions in water. Nature performs a multitude of chemical transformations in water under mild conditions mediated by enzymes. In particular the nanoconfinement effects of the enzymes ensure high activity and impressive stereoselectivities. Micellar catalysis is nowadays a real alternative approach to catalysis in traditional organic media, enabling good activity under mild conditions, with the advantage of possible catalyst and micellar medium recycling. Micellar media emerged also as good nano‐environments for stereoselective reactions, with many examples of chemical transformations mediated by metal and organo‐catalysts for which improvements of stereoselectivity were observed with respect to the same reaction under homogeneous conditions in traditional organic solvents. More specifically, both the catalytically active site and the micelles provided by the surfactant can contribute to the asymmetric induction, partially resembling what known in terms of stereoselectivity imparted by the active site of enzymes and metallo‐enzymes.magnified image

The impact of using recycled culture medium to grow Chlorella vulgaris in a sequential flow system: Evaluation on growth, carbon removal, and biochemical compositions

Excessive of carbon dioxide (CO2) emission and water pollution have been identified as the two primary challenges to humans and environment. Hence, biological carbon sequestration by microalgae is recommended as an environmentally friendly approach to capture and convert this CO2 into value-added products. However, research related to the development of efficient system to concurrently overcome low CO2 solubility in water and reduction of water footprint in microalgae cultivation is still limited in the literature. In this study, the CO2 capture by Chlorella vulgaris in a recycled cultivation medium was exploited using a sequential flow photobioreactor system. The study revealed that nutrient replenished recycled medium did not significantly affect the growth performance and lipid content of C. vulgaris. It was also observed that the CO2 capture efficiency and protein content were gradually increased from the first (SFB-RWN1) to the third (SFB-RWN3) cycle of cultivation due to the increment of carbon and nitrogen content in the microalgae cell. Besides, the lipid profile of C. vulgaris cultivated in the recycled medium comprised of high concentration of saturated (up to 32.41%) and polyunsaturated (up to 43.21%) fatty acid methyl ester (FAME). The present study suggested that growing C. vulgaris in a recycled medium is a feasible solution to fix CO2 from the atmosphere and help to reduce water footprint in the microalgae cultivation system.

Microalgae Culture Medium Recycling: Improved Production of Biomass and Lipids, Biodiesel Properties and Cost Reduction

Microalgae Culture Medium Recycling: Improved Production of Biomass and Lipids, Biodiesel Properties and Cost Reduction

The Feasibility Research on Reusing High Salinity Wastewater as a Plant Nutrient Medium for Plant Hydroponics in CELSS

The reuse of wastewater is a key problem in controlled ecological life support system (CELSS). In this study, the feasibility to reuse the treated wastewater (including sanitary wastewater and urine wastewater) as a plant hydroponic medium was verified. Two salt-tolerant plants, apium graveolens Linn (celery) and mesembryanthemum cordifolium L.F. (cordifolium), were cultivated with the reused medium or Hoagland nutrient solution, and the characteristics of crop growth, hydroponic medium composition, and elements absorption by plants were investigated. The results showed that the reused medium replenished with micronutrient elements could maintain the normal growth of cordifolium and celery crops. The biomass productivity of cordifolium cultivated by the recycled medium (121.53 g FW/strain) was higher than that cultivated by Hoagland nutrient solution (98.33 g FW/strain). The nutrient elements accumulation in plant dry mass indicated that plants could effectively utilize the recycled mineral elements in wastewater, and cordifolium exhibited better stability and adaptability to salt-induced environment. The absorption capacity of Na and Cl elements in cordifolium cultivated within the reused medium was the highest, which was 4.54% DW and 2.63% DW, respectively. This study demonstrated the feasibility to directly reuse domestic wastewater as the main ingredient for plant hydroponics, which could provide insights into design and operation of plant hydroponics system and water circulation system in CELSS.

Synergistic integration of wastewaters from second generation ethanol plant for algal biofuel production: an industrially relevant option.

The present study provides an integrated method for utilizing the wastewaters from second generation (2G) ethanol pretreatment plant for microalgal biomass and lipid production. The study was conducted using a mixture of wastewaters (referred as MW; pH 4.3) generated after washing of acidic and alkaline-soaked lignocellulosic biomass prior to pretreatment process. The growth studies indicated that the thermotolerant strain of Chlorella pyrenoidosa (C. pyrenoidosa) M18 exhibited higher cell proliferation in wastewater as compared to freshwater. About 20-25% enhancement in biomass (509mg L-1 d-1 ± 3.09) and lipid productivity (146mg L-1 d-1 ± 1.34) was observed in MW. The total chlorophyll content and variable fluorescence by maximum fluorescence (Fv/Fm) ratio of strain cultivated in MW were 10.32µgmL-1 and 0.75, respectively. The use of MW also enhanced the content of saturated and monounsaturated fatty acids in total lipid. The exhausted wastewater medium obtained after harvesting the auto-flocculated biomass was also reused up to three successive growth cycles. The recycled medium without any nutrient addition could be used for two subsequent rounds with enhanced biomass (520mg L-1 d-1 ± 4.07) and lipid (157.71mg L-1 d-1 ± 1.09) productivities. This synergistic approach of cultivating thermotolerant microalgae with wastewater from 2G pretreatment plant provides an economical setup for development of commercial algal biofuel technology.

Effect of medium recycling, culture depth, and mixing duration on D. salina growth

Microalgal cultivation is currently stifled by various constraints. In winter, additional losses are incurred due to lower productivities. Here, effects of medium recycling to conserve water use, paddle wheel mixing duration to reduce power consumption and culture depth on growth of Dunaliella salina (MUR 8) cultivated in raceway ponds during the Austral winter season was studied. Ponds were operated semi-continuously at 0.18 m depth to study the effect of medium recycling on the growth and productivity. One pond served as a control without recycling (NMR) which was replenished with fresh medium after each harvest while the other served as a test variable with medium recycling (MR). In parallel, two ponds were also operated to investigate the effects of culture depth on the growth and productivity with one pond being operated at of 0.11 m (LD) and the other at 0.18 m (HD). Subsequently, a comparison of 24 h paddle wheel mixing (24MX) against 12 h daytime paddle wheel mixing (12MX) was also performed in 2 m2 raceway ponds. Our results showed that medium recycling, paddlewheel mixing time and pond depth did not have significant effects on μmax, biomass, lipids, and carotenoid productivity of Dunaliella salina. However, carotenoids: chlorophyll a ratio were significantly higher in LD treatments in comparison with HD treatments. Areal productivities were also higher in HD treatments compared to LD treatments. Medium recycling, paddlewheel mixing time and pond depth also had no significant effect on the photosynthetic parameters: Fv′/Fm′, rETRmax and Ioptimum. However, α was higher in HD treatments compared to LD treatments. NPQmax was also higher in 24MX treatments compared to 12MX treatment. In here we demonstrated that medium recycling and reduced paddle wheel mixing could be employed as viable cost and energy saving methods in the cultivation of Dunaliella salina during the Austral winter season.

Cultivation of Chlorella vulgaris in Sequential Flow Photobioreactor System: Influence of Recycled Culture Medium on Growth, Lipid and Protein Content

In the present work, the reusability of culture medium to grow Chlorella vulgaris was examined in an effort to reduce the freshwater footprint of microalgae cultivation. The microalagae was cultivated in a sequential-flow system equipped with five photobioreactors connected in series. Furthermore, the effect of recycled culture medium without additional nutrients on the growth, lipid and protein content of microalgae was evaluated under optimized cultivation conditions. Experimental results showed that biomass concentration and growth rate reduced when the recycled culture medium was used. The maximum biomass concentration was achieved in the fresh medium with a total biomass yield of 1.42 g/L. Meanwhile, lipid content was found to increase when the microalgae was cultivated in the recycled medium, in which the highest lipid content (58.01 wt.%) was attained from photobioreactor 5 (cycle 2). On the contrary, the protein content (11.98 wt.%) of the microalgae in the recycled medium was considerably lower than the fresh medium (49.20 wt.%). These results suggested that the reuse of culture medium to grow microalgae is possible, however, it has a significant impact on the biochemical compositions of Chlorella vulgaris. Therefore, it is important to determine the desired product prior to reusing the medium for subsequent cultivation process.

Hydrodynamic cavitation for bacterial disinfection and medium recycling for sustainable Ettlia sp. cultivation

Open cultivation systems are the most economic option for microalgal biomass production but their harvesting cost, bacterial invasion, and water usage are still deterring large-scale applications. Therefore, in this study, low-cost techniques for harvesting, bacterial disinfection, and medium recycling were sequentially implemented for Ettlia sp. For harvesting, the employed auto-flocculation harvested 96% of algae but was not able to remove bacteria that invaded during cultivation. For this reason, hydrodynamic treatment was applied as a bacterial disinfection method for medium recycling, and treated up to 100% of the bacteria in the supernatant. Afterward, the supernatant was replenished with nutrients and reused to grow microalgae. In medium-recycled cultivation, auto-flocculation recycled (AR) medium showed the highest final biomass concentration of 3.84 g L−1, while the centrifugation recycled (CR) medium and the fresh medium (FM) resulted in 3.78 and 3.67 g L−1, respectively. In addition, the lipid content of the AR group was highly increased to 20.4%, resulting in the highest lipid productivity of 0.11 g L−1 d−1. Moreover, an analysis of fatty acid methyl ester compositions confirmed that 76.6% of lipid from the AR group were mainly composed of C16-C18, which are suitable for biodiesel. Consequently, the results showed that the implementation of low-cost techniques not only reduced process costs and water usage but also enhances both the biomass and lipid productivities of the species.

Interpreting pre-vegetation landscape dynamics: The Cambrian Lower Mount Simon Sandstone, Illinois, U.S.A.

ABSTRACTThe Cambrian Mount Simon Sandstone has been the subject of extensive study and multiple industrial-scale carbon storage demonstrations at Decatur, Illinois, USA. The development of a reliable paleoenvironmental model is critical to successful large-scale carbon dioxide (CO2) storage, but is complicated by the need to interpret pre-vegetation sedimentation processes. The present study presents a paleoenvironmental model of the Lower Mount Simon Sandstone, based on analysis of primary sedimentary structures in two cores and four complete high-resolution resistivity logs (FMI).The Lower Mount Simon Sandstone represents a vertical “drying-up” sequence composed of three associated depositional units: a north–south oriented coastal system at the base, an eastward-directed fluvial unit in the middle, and a westward-directed eolian system at the top that recycled medium- and fine-grained sand in the basin. Quantitative analysis of fluvial cross-strata indicates that the perennial river system was shallow (c. 1 m deep) with relatively narrow channel belts (c. 1 km). Adjacent sandy eolian-floodplain deposits contain abundant thin, crinkly planar laminae that are enriched in fines and are interpreted as cementation surfaces, likely of biological origin. Deflation lags and wind-ripple strata are commonly interbedded with the crinkly strata, suggesting that the recurrence of erosion and deposition that controlled sedimentary preservation on the floodplain were dominated by eolian transport, re-wetting, and (bio-) cementation. Such a prominent role of exposure to the wind, basin-scale sediment recycling, and eolian removal of fine-grained sediment would have ceased to exist for most climates after the development of vegetation on land, yet, may well be key to understanding the environmental context for early life on Earth.

Optimization by response surface methodology for production of β-galactosidase from Enterococcus faecium using recycled medium

In this study, recycled medium from three photosynthetic microorganisms (Chlorella vulgaris, Dunaliella tertiolecta and Arthrospira platensis) was evaluated for use in producing β-galactosidase, an enzyme traditionally used to degrade lactose in dairy products. Recycled medium from Chlorella vulgaris was selected to optimize culture medium to be used to produce β-galactosidase by Enterococcus faecium in submerged fermentation. Response Surface Methodology (RSM) was used to optimize the levels of the variables: temperature (30-40°C), lactose concentration (0-5%), fermentation time (12-24h), pH (6-8) and their interaction. All variables studied had a statistically significant effect on the production of β-galactosidase. The optimal conditions for producing the enzyme were achieved: temperature of 31ºC, lactose concentration of 5.34%, fermentation time of 12h and pH of 8.0. Under these conditions, the β-galactosidase activity was 29.85 U/mL which was quite close to the predicted value (30.83 U/mL). Finally, it can be concluded that recycled medium from optimized C. vulgaris supernatant may well be important for the biotechnology industry as it is an abundant low-cost source for producing β-galactosidase by Enterococcus faecium.