Statistical Optimization of Alkali Pretreatment to Improve Sugars Recovery from Spent Coffee Grounds and Utilization in Lactic Acid Fermentation

Abstract

Biorefinery, which utilizes carbon-neutral biomass as a resource, is attracting attention as a significant alternative in a modern society confronted with climate change. In this study, spent coffee grounds (SCGs) were used as the feedstock for lactic acid fermentation. In order to improve sugar conversion, alkali pretreatment was optimized by a statistical method, namely response surface methodology (RSM). The optimum conditions for the alkali pretreatment of SCGs were determined as follows: 75°C, 3% potassium hydroxide (KOH) and a time of 2.8 h. The optimum conditions for enzymatic hydrolysis of pretreated SCGs were determined as follows: enzyme complex loading of 30-unit cellulase, 15-unit cellobiase and 50-unit mannanase per g biomass and a reaction time of 96 h. SCG hydrolysates were used as the carbon source for Lactobacillus cultivation, and the conversions of lactic acid by L. brevis ATCC 8287 and L. parabuchneri ATCC 49374 were 40.1% and 55.8%, respectively. Finally, the maximum lactic acid production by L. parabuchneri ATCC 49374 was estimated to be 101.2 g based on 1000 g of SCGs through the optimization of alkali pretreatment and enzymatic hydrolysis.

Improvement of Enzymatic Glucose Conversion from Chestnut Shells through Optimization of KOH Pretreatment

“…It has also been an effective method for high glucose yield after enzymatic hydrolysis. Other reports also confirmed this phenomenon, and it was almost founded in the reaction conditions within 3 h of 3% KOH, 75-121 • C [44][45][46]. The CNS used in this study is rich in carbohydrates that can serve as substrates in the fermentation process.…”

“…The recent studies that focus on the optimization of alkali pretreatment are summarized in Table 7. The pretreatment of various biomass such as canola straw, Sida acuta (Thailand Weed), Sicyos angulatus, Miscanthus, bamboo, corncob, walnut shell, corn stover, orange peel and spent coffee ground (SCG) were carried out under the determined conditions using alkali reagents (NaOH, NH 3 and KOH) [17,18,22,[41][42][43][44][45][46]. The reported data such as the solid components and enzymatic digestibility before and after the pretreatments were investigated.…”

Enhanced Production of Bacterial Cellulose from Miscanthus as Sustainable Feedstock through Statistical Optimization of Culture Conditions

“…The statistical acceptability of the predictive model was assessed using the coefficient of determination (R 2 ), and a value close to 1 indicates that the experimental response agrees with the predicted response within the designed experimental range [ 30 ]. The R 2 values higher than 0.8 and a difference between R 2 and adjusted R 2 not exceeding 0.2 indicate the reliability of the model [ 31 ]. The R 2 and adjusted R 2 of our model were 0.9579 and 0.9200, respectively, indicating the statistical acceptability of our model.…”

Rapid and concise quantification of mycelial growth by microscopic image intensity model and application to mass cultivation of fungi

“…The inoculum (4%, v/v) of seed broth of C. militaris KYL05 was transferred into the main medium. The cultivation was performed in a 250 mL Erlenmeyer flask containing 50 ml of broth main medium at 25 °C for six days in a shaking incubator (150 rpm) 11 , 20 , 42 .…”