Department of Chemical Engineering, Gazi University, Maltepe, Ankara, Turkey.
Bioresour Technol. 2010 Nov;101(22):8664-70. doi: 10.1016/j.biortech.2010.05.085.
In this study, we investigated the use of hazelnut shell as a renewable and low cost lignocellulosic material for bioethanol production for the first time. High lignin content of hazelnut shell is an important obstacle for such a biotransformation. Biomass hydrolysis with acids yields reducing sugar with several inhibitors which limit the fermentability of sugars. The various conditioning methods for biomass and hydrolysate were performed to overcome the toxicity and their effects on the subsequent fermentation of hazelnut shell hydrolysate by Pichia stipitis were evaluated with shaking flasks experiments. Hazelnut shells hydrolysis with 0.7M H(2)SO(4) yielded 49 gl(-1) total reducing sugars and fermentation inhibitors in untreated hydrolysate. First, it was shown that several hydrolysate detoxification methods were solely inefficient in achieving cell growth and ethanol production in the fermentation of hazelnut shell hydrolysates derived from non-delignified biomass. Next, different pretreatments of hazelnut shells were considered for delignification and employed before hydrolysis in conjunction with hydrolysate detoxification to improve alcohol fermentation. Among six delignification methods, the most effective pretreatment regarding to ethanol concentration includes the treatment of shells with 3% (w/v) NaOH at room temperature, which was integrated with sequential hydrolysate detoxification by overliming and then treatment with charcoal twice at 60 degrees C. This treatment brought about a total reduction of 97% in furans and 88.4% in phenolics. Almost all trialed treatments caused significant sugar loss. Under the best assayed conditions, ethanol concentration of 16.79gl(-1) was reached from a hazelnut shell hyrolysate containing initial 50g total reducing sugar l(-1) after partial synthetic xylose supplementation. This value is equal to 91.25% of ethanol concentration that was obtained from synthetic d-xylose under same conditions. The present study demonstrates that Pichia stipitis is able to grow and ferment sugars to ethanol in detoxified hazelnut hydrolysate derived from delignified biomass.
本研究首次探索了榛子壳作为可再生且低成本的木质纤维素原料用于生物乙醇生产。榛子壳中高含量的木质素是实现这种生物转化的重要障碍。生物质用酸水解会产生含有多种抑制剂的还原糖，这些抑制剂会限制糖的发酵性。为了克服毒性，对生物质和水解物进行了各种调节方法，并通过摇瓶实验评估了它们对毕赤酵母发酵榛子壳水解物的后续影响。用 0.7M H2SO4 水解榛子壳可得到 49g/L 的总还原糖和未处理水解物中的发酵抑制剂。首先，结果表明，几种水解物解毒方法单独使用时，在发酵未木质素化生物质衍生的榛子壳水解物时，无法实现细胞生长和乙醇生产。接下来，考虑了几种榛子壳预处理方法用于脱木质素，并在水解前与水解物解毒相结合，以提高酒精发酵。在 6 种脱木质素方法中，最有效的预处理方法是在室温下用 3%（w/v）NaOH 处理壳，然后通过过石灰处理和 60°C 下两次活性炭处理进行顺序水解物解毒。这种处理使呋喃的总量减少了 97%，酚类物质减少了 88.4%。几乎所有的处理方法都导致了糖的大量损失。在最佳测定条件下，从含有初始 50g/L 总还原糖的榛子壳水解物中，通过部分补充合成木糖，可获得 16.79g/L 的乙醇浓度，相当于在相同条件下从合成 d-木糖获得的乙醇浓度的 91.25%。本研究表明，毕赤酵母能够在脱毒的木质素化生物质衍生的榛子水解物中生长并将糖发酵为乙醇。
