Volatile fatty acids production from cheese whey: influence of pH, solid retention time and organic loading rate

Abstract

BACKGROUND The influence of pH, sludge retention time (SRT) and organic loading rate (OLR) were evaluated in the fermentation of cheese whey to produce volatile fatty acids (VFA) in a sequencing batch reactor (SBR). The reactor performance was studied at SRT of 4, 6 and 10 days and the influence of pH (5, 5.5 and 6) was determined at each SRT. The OLR effect was also studied in the range 3 to 12 g COD L‐1 d‐1, while keeping the other parameters mentioned above constant. RESULTS A more acidic pH , improved the degree of acidification at short SRT (4 and 6 days), reaching 76 and 84%, respectively, meanwhile at pH 6 the degree of acidification (DA) improved and reached 85% at longer SRT (10 d). Regarding the VFA profile, a pH shift from 5 to 6 stimulated the production of acetic and propionic acids, whereas the production of butyric and valeric acids decreased irrespective of the SRT applied. Moreover, the increase of SRT from 4 to 10 d boosted propionic and valeric acids production regardless of the pH applied. Lower OLR favoured the production of propionic and valeric acids, while higher OLR increased the production of butyric acid. Lactose degradation and VFA production followed the Michaelis–Menten model. CONCLUSION A selective VFA distribution can be reached by modifying parameters such as pH, SRT and OLR in acidogenic reactors, therefore, they could be suitable for further valorisation purposes in the production of polyhydroxyalkanoates from such VFA. © 2017 Society of Chemical Industry

An Unstructured Model for Anaerobic Treatment of Raw Cheese Whey for Volatile Fatty Acids Production

“…All experimental runs were performed in duplicate, using fresh raw cheese whey as a substrate collected from a community dairy located in Coacoatzintla Veracruz, México. The process operation was carried out under mesophilic conditions, considering two temperatures, 35 and 40 • C, and two pH values, 5.5 and 7.5. pH, and temperature values coincide with the reported conditions, where the operation is stable and VFA production is favored [7,26,27].…”

“…Table 1 shows the physicochemical characteristics of the fresh raw cheese whey and inoculum used in the experimental tests. It is observed that COD is significantly higher than reported by Gelegenis et al [44] and Calero et al, [7]. The inoculum showed a COD = 32.5 g COD L −1 , where 28.56 g L −1 corresponds to VFA, while the protein concentration was 7.22 g L −1 and carbohydrate concentration was 0.94 g L −1 .…”

“…According to the prediction of the model, it can be observed that the conditions that favor the VFA production using raw crude whey are at a neutral or alkaline pH and temperature above 40 • C. Under controlled pH conditions, it has been reported that the conditions that favor the VFA generation using whey as substrate should be a slightly acidic pH (pH = 5.5-6) at mesophilic conditions (T = 35-37 • C) [7,26,27]. However, if pH is not controlled, the system naturally self-regulates under alkaline conditions and VFA production is favored at pH ≥ 7.…”

“…In general, the variables that have an impact on the overall stability of the process are the oxidation state of carbon in the substrate, pH, and temperature, as well as the hydraulic retention time (HRT) and the reactor set-up. For example, Calero et al [7] evaluated the influence of pH, sludge retention time (SRT) and organic loading rate (OLR) in the fermentation of cheese whey to produce volatile fatty acids (VFA), finding that, depending on the operating conditions, different types of VFA are generated. For pH conditions between 5 and 6, the production of acetic and propionic acids is favored.…”

“…Recent works on the anaerobic treatment of cheese whey have been published [22][23][24], however the determination of the operating conditions that favor VFA production using raw whey has been poorly addressed. In addition, the reported works suggest a pretreatment of cheese whey prior to anaerobic treatment with the purpose of increasing the degradability of the substrate and favoring the by-product generation [2,7,25]. Nevertheless, pretreatment increases the number of unit operations, so its potential application in small and medium industries can be limited.…”