The Bioconversion of Pretreated Cashew Apple Bagasse into Ethanol by SHF and SSF Processes

Ethanol production from acidic-alkaline pretreated cashew apple bagasse (CAB-OH) was investigated using separated hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes. First, a screening of Kluyveromyces strains was conducted by SHF and a maximum ethanol concentration of 24.1 g L(-1) was obtained using Kluyveromyces marxianus ATCC36907, which presented similar profiles when compared to results obtained by a Saccharomyces strain. The effect of temperature on ethanol production conducted by SHF using K. marxianus ATCC36907 was investigated, and the maximum ethanol yield (YE/G) was obtained at 40 °C (0.46 g g(-1)) using a synthetic medium. In the SHF using CAB-OH hydrolysate, the maximum ethanol concentration obtained was 24.9 g L(-1), 5.92 g L(-1) h(-1) of productivity, and ethanol yield of 0.43 g g(-1) at 40 °C. Afterwards, K. marxianus ATCC36907 was used in the bioconversion of CAB-OH by SSF, and an ethanol concentration of 41.41 ± 0.2 g L(-1) was obtained using 10 % CAB-OH at 40 °C, 150 rpm and 24 h, resulting in a Y'E/G of 0.50 gE gG (-1) and an efficiency of 98.4 %, in the process conducted with cellobiase supplementation. SHF and SSF processes using CAB-OH and K. marxianus ATCC36907 can be used to ethanol production, but the SSF process required only one step to achieve the same production.