Direct processing of alginate-immobilized microalgae into polyhydroxybutyrate using marine bacterium of Saccharophagus degradans.

Alginate immobilized microalgae (AIM) was found efficient in algal cells separation and pollutants removal, however, its processing required alginate removal. In present study, polysaccharide-degrading bacterium of Saccharophagus degradans was used to biodegrade alginate and microalgae in AIM and produce polyhydroxybutyrate (PHB). Results showed that AIM cultivated in wastewater contained 34.0% carbohydrate and 45.7% protein. S. degradans effectively degraded and utilized polysaccharide of AIM to maintain five-day continuous growth at 7.1-8.8 log CFU/mL. Compared with glucose, S. degradans metabolism of mixed polysaccharide in AIM maintained the medium pH at 7.1-7.8. Increasing the inoculum concentration did not enhance AIM utilization by S. degradans due to the carbon catabolite repression of glucose which likely inactivated hydrolysis enzymes. PHB production in S. degradans peaked at 64.9 mg/L after 72 h cultivation but was later degraded to provide energy. Conclusively, S. degradans was effective in direct processing of AIM while showing potential in PHB production.

Integration of ozone with co-immobilized microalgae-activated sludge bacterial symbiosis for efficient on-site treatment of meat processing wastewater.

Direct discharge of high concentration meat processing wastewater (MPW) into municipal sewage system will cause serious shock loading and reduce wastewater treatment efficiency, thus, efficient on-site pretreatment is usually required. Purpose of this study is to integrate ozone with microalgal biotreatment to achieve effective removal of both organic compounds and nutrients with one-step biodegradation and obtain high quality effluent dischargeable to municipal sewage system. Results showed that ozone pretreatment removed 35.0-90.2% color and inactivated 1.8-4.7 log CFU/mL bacteria in MPW. In post biotreatment using microalgae co-immobilized with activated sludge (ACS) bacteria, bacterial growth in ozone pretreated wastewater (7.1-8.1 log CFU/mL) were higher than non-pretreated control (6.0 log CFU/mL) due to enhanced biodegradability of wastewater pollutants. Algal biomass growth in wastewater pretreated with 0.5 (2489.3 mg/L) and 1 (2582.0 mg/L) minute's ozonation were improved and higher than control (2297.1 mg/L). Ozone pretreatment significantly improved nutrients removal. Following ozone pretreatment of 0.5 min, microalgal biotreatment removed 60.1% soluble chemical oxygen demand (sCOD), 79.5% total nitrogen (TN) and 91.9% total phosphate (PO43-) which were higher than control (34.4% sCOD, 63.4% TN, 77.6% total PO43-). Treated effluent contained 342.3 mg/L sCOD, 28.8 mg/L TN, 9.9 mg/L total PO43- and could be discharged into municipal sewage system. However, excessive ozone pretreatment displayed adverse impact on algal growth and sCOD removal. Therefore, integration of 0.5 min's ozone pretreatment with microalgae-based biotreatment is an efficient on-site treatment to simultaneously remove organic compounds and nutrients with one-step biodegradation.

Integration of sodium hypochlorite pretreatment with co-immobilized microalgae/bacteria treatment of meat processing wastewater.

Wastewater with 0.2, 0.4, 0.8, 1.0 mg/L free chlorine was biologically treated using co-immobilized microalgae/bacteria. In contrast, non-pretreated wastewater was treated with beads (control) and blank beads (blank) under the same operating condition. Results showed that NaClO pretreatment removed 8-33% total nitrogen (TN), 31-45% true color and 0.7-2.5 log CFU/mL aerobic-bacteria. At the end of treatment, maximum algal biomass (2,027 dry weight mg/L) was achieved with 0.2 mg/L free chlorine. Bacterial growth in wastewater was decreased by NaClO pretreatment before reaching 7.2-7.7 log CFU/mL on the fifth day. Beads with microorganisms (control) removed 15% more chemical-oxygen-demand (COD), 16% more TN, and 13% more total phosphate (PO43-) than blank. Pretreatment with 0.2 mg/L free chlorine increased TN removal from 75% to 80% while pollutants removal was substantially decreased with 0.4-1.0 mg/L free chlorine. Considering algal biomass growth and pollutants removal, 0.2 mg/L free chlorine pretreatment was recommended for microalgae/bacteria co-immobilized system.

Risk-based assessment and criteria specification of the microbial safety of wastewater reuse in food processing: Managing Listeria monocytogenes contamination in pasteurized fluid milk.

Intense pressure on water resources has led to efforts to reuse reclaimed processing wastewater for cleaning purposes in food processing plants. The milk industry produces considerable amounts of wastewater, which can be used for cleaning of equipment after appropriate treatment. However, due to naturally occurring microbiological contamination in raw milk, the wastewater is often contaminated, and therefore the reuse of reclaimed wastewater is perceived as risky. This study aims to quantify the risks of Listeria monocytogenes infection and associated disease burden when wastewater reclaimed from milk processing operations is used in cleaning-in-place (CIP) systems for pasteurized fluid milk production following a quantitative microbial risk assessment (QMRA) approach. Furthermore, this study aims to inform risk-based tolerable limits for levels of contamination in CIP water based on a public health target of 10-6 DALY per person annually. The suggested model investigates the passage of L. monocytogenes throughout the fluid milk chain, from receipt of raw milk at the plant to the point of consumption and covering storage in receiving and storage tanks, pasteurization, and storage at retail and at home. Risk and disease burden estimates are simulated for general (younger than 65 years), elderly (65 years and older) and pregnant population subgroups. Additional scenarios covering the effect of using clean water, using water with different levels of contamination and using reclaimed wastewater modeled as recovered from cheese whey after membrane filtration (reclaimed water scenario) are considered to estimate a risk-based limit of contamination and simulate a real-life example. The tolerable limit of contamination in CIP water was estimated as -2 log10 CFU/mL to ensure the protection of the most vulnerable subgroup, pregnant women, while higher limits were estimated for the elderly and general subgroups. Under the reclaimed water scenario, the annual number of listeriosis cases was estimated as 3.36, 5.67, and 0.15 for the general, elderly and pregnant population subgroups, respectively, while in the clean water scenario, the estimates were 3.33, 5.56 and 0.15, respectively. In both scenarios, the DALY estimates were lower than the tolerable limit. The results indicate that reclaimed water can be an alternative to potable water for CIP applications.

Feasibility, safety, and economic implications of whey-recovered water in cleaning-in-place systems: A case study on water conservation for the dairy industry.

Water scarcity is threatening food security and business growth in the United States. In the dairy sector, most of the water is used in cleaning applications; therefore, any attempt to support water conservation in these processes will have a considerable effect on the water footprint of dairy products. This study demonstrates the viability for recovering good quality water from whey, a highly pollutant cheese-making by-product, to be reused in cleaning-in-place systems. The results obtained in this study indicate that by using a combined ultrafiltration and reverse osmosis system, 47% of water can be recovered. This system generates protein and lactose concentrates, by-products that once spray-dried fulfill commercial standards for protein and lactose powders. The physicochemical and microbiological quality of the recovered permeate was also analyzed, suggesting suitable properties to be reused in the cleaning-in-place system without affecting the quality and safety of the product manufactured on the cleaned equipment. A cost analysis was conducted for 3 cheese manufacturing levels, considering an annual production of 1, 20, and 225 million liters of whey. Results indicate the feasibility of this intervention in the dairy industry, generating revenues of $0.18, $3.05, and $33.4 million per year, respectively. The findings provide scientific evidence to promote the safety of reuse of reconditioned water in food processing plants, contributing to building a culture of water conservation and sustainable production throughout the food supply chain.