Two-Step Process Using Immobilized Saccharomyces cerevisiae and Pichia stipitis for Ethanol Production from Ulva pertusa Kjellman Hydrolysate

Abstract

We established a two-step production process using immobilized S. cerevisiae and P. stipitis yeast to produce ethanol from seaweed (U. pertusa Kjellman) hydrolysate. The process was designed to completely consume both glucose and xylose. In particular, the yeasts were immobilized using DEAE-corncob and DEAE-cotton, respectively. The first step of the process included a continuous column reactor using immobilized S. cerevisiae, and the second step included a repeated-batch reactor using immobilized P. stipitis. It was verified that the glucose and xylose in 20 L of medium containing the U. pertusa Kjellman hydrolysate was converted completely to about 5.0 g/l ethanol through the two-step process, in which the overall ethanol yield from total reducing sugar was 0.37 and the volumetric ethanol productivity was 0.126 g/ l/h. The volumetric ethanol productivity of the two-step process was about 2.7 times greater than that when P. stipitis was used alone for ethanol production from U. pertusa Kjellman hydrolysate. In addition, the overall ethanol yield from glucose and xylose was superior to that when P. stipitis was used alone for ethanol production. This two-step process will not only contribute to the development of an integrated process for ethanol production from glucose and xylose-containing biomass hydrolysates, but could also be used as an alternative method for ethanol production.

Ethanol Production from Glycerol Using Immobilized Pachysolen tannophilus During Microaerated Repeated-Batch Fermentor Culture

“…Immobilization of yeast cells using DEAE (2-(diethylamino)ethyl chloride hydrochloride)-corncob and DEAE-cotton was conducted according to the protocols previously described in detail [9,10].…”

“…The flask cultures were performed using 100 ml Erlenmeyer flasks in a shaking incubator at 30 o C and 150 rpm. The protocols for the flask cultures of yeast immobilized on DEAE-corncob and DEAE-cotton were described in detail in previous reports [9,10].…”

“…Scanning electron microscopy (ESEM; FEI Quanta 400, Hillsboro, OR, USA) observations were made after the yeast cell-immobilized Celite was washed with deionized water and dried for 24 h at 60°C [9,10].…”

“…The immobilization methods for yeast were compared in view of operational durability for cell adsorption and ethanol production, as these variables are necessary for the long-term operation of an ethanol-producing system. In particular, Celite (a trademarked brand name of diatomaceous earth) was investigated as the carrier for the immobilization of P. tannophilus, together with DEAE-corncob [10] and DEAE-cotton [9]. Celite has sometimes been used as an immobilization carrier of yeast cells and enzymes [7,17].…”

Evaluating Carriers for Immobilizing Saccharomyces cerevisiae for Ethanol Production in a Continuous Column Reactor

“…Among agricultural waste materials, sorghum bagasse [ 6 ], sugarcane pieces [ 7 ], orange peel [ 8 ], apple bagasse [ 9 ], corncobs [ 10 , 11 ], and sawdust [ 12 ] have been reported as immobilization carriers for S. cerevisiae because of their low price and high availability. In our previous studies, we investigated corncob and cotton as carriers for immobilization of S. cerevisiae in ethanol production [ 13 , 14 ]. However, to further decrease the cost of production of ethanol, it is necessary to explore other carrier options to immobilize yeast cells.…”