Single-Step Ethanol Production from Raw Cassava Starch Using a Combination of Raw Starch Hydrolysis and Fermentation, Scale-Up from 5-L Laboratory and 200-L Pilot Plant to 3,000-L Industrial Fermenters

Abstract

Background: A single-step ethanol production is the combination of raw cassava starch hydrolysis and fermentation. For the development of raw starch consolidated bioprocessing (CBP) technologies, this research work was to investigate the optimum conditions and technical procedures for the production of ethanol from raw cassava starch in a single step. This resulted high yields and productivities of all the experiments from the laboratory, the pilot, through the industrial scales. The yields of ethanol concentration are comparable with those in the commercial industries that use molasses and hydrolyzed starch as the raw materials. Results: Before single-step ethanol production, the studies of raw cassava starch hydrolysis by a granular starch hydrolyzing enzyme, StargenTM002, were carefully conducted. It successfully converted 80.19% (w/v) of raw cassava starch to glucose at a concentration of 176.41 g/L with a productivity of 2.45 g/L/h when the raw starch was pretreated at 60 °C for 1 h with 0.10% (v/w dry starch basis) of Distillase ASP before hydrolysis. A single-step ethanol production at 34 °C in a 5-L fermenter showed that S. cerevisiae (Fali, active dry yeast) produced the maximum ethanol concentration, p of 81.86 g/L (10.43% v/v) with a yield coefficient, Y p/s of 0.41 g/g, a productivity or production rate, r p of 1.14 g/L/h with an efficiency, Ef of 71.44%. The scale-up experiments of the single-step ethanol production using this method, from the 5-L fermenter to the 200-L fermenter and further to the 3,000-L industrial fermenter were successfully achieved with essentially good results. The p, Y p/s , r p , and Ef values of the 200-L scale were 80.85 g/L (10.23% v/v), 0.41 g/g, 1.12 g/L/h and 72.47% , respectively ; of the 3,000-L scale were 70.74 g/L (9.01% v/v), 0.34 g/g, 0.98 g/L/h and 59.82% , respectively. Because of using raw starch, the major by-products of all the three scales were very low; glycerol lactic acid and acetic acid, in ranges of 0.94-1.14%, 0.046-0.052%, 0-0.059% (w/v), respectively, where are less than those values in the industries. Conclusions: This single-step ethanol production using a combination of raw cassava starch hydrolysis and fermentation of the three fermentation scales here is practicable and feasible for the scale-up of industrial production of ethanol from raw starch.

Utilization of Indonesian root and tuber starches for glucose production by cold enzymatic hydrolysis

“…This enzyme is an optimized blend of Aspergillus kawachi α-amylase and a glucoamylase from Trichoderma reesei (Genencor 2008). To date, most research has been conducted on Stargen™ 002 to improve the liquefaction and saccharification steps in the glucose and bioethanol production from grain crops such as corn, rice, and wheat starch (Adams et al 2011;Chu-Ky et al 2015;Kuhn et al 2015;Strąk-Graczyk et al 2019;Tse et al 2021) or cassava (Krajang et al 2021;Tse et al 2021). To our knowledge, the information available on the enzymatic saccharification of tropical raw starches using Stargen™ 002 at below gelatinization temperature is still limited (Hargono et al 2018;Krajang et al 2021).…”

Somatic embryogenesis in two cassava (Manihot esculenta Crantz) genotypes

“…However, starch content is most important as it can be used as raw material for production of ethanol and other industries 2 (Uchechukwu- Agua et al, 2015). It has been well documented that the starch derived from cassava is more better for conversion to biofuels as compare to other starch such as corn, wheat, and rice (Krajang et al, 2021). Furthermore, the plant has been reported as a major source of calorie in country like Africa (FAO, 2020) and major source of starch in some Asian (Howeler, 2012) as well as in American countries (Aristizabal et al, 2017).…”