木薯渣分批补料酶水解及酒精发酵的研究

木薯渣是木薯淀粉加工后的废弃物,碳水化合物含量高。实验利用复合酶对木薯渣中淀粉和纤维素等碳水化合物非热水解进行了探索,结果表明:木薯渣具有较好的酶解性能;随着底物浓度的增大,酶解液糖浓度也不断提高,酶解得率逐渐降低;与间歇糖化工艺相比,16%底物在相同的水解条件和相同的酶添加量的条件下,采用4%的起始底物浓度,每隔12 h进行补料,葡萄糖得率从53.6%提高到72.4%;以不添加任何营养物质的水解液为原料进行酒精发酵,24h乙醇浓度达到24.9 g/L,乙醇得率达到42%,发酵效率为82%,乙醇产率达到1.04 g/(L.h),葡萄糖利用率达到97%。     

Influence of Cassava Storage Root Development and Environmental Conditions on Starch Granule Size Distribution

Among starch producing crops, cassava has a higher carbohydrate production than others under suboptimal conditions, more than 163×10⁶ t of cassava starch are produced world‐wide each year and are used for direct human consumption, animal feeds and as raw material for a wide range of industrial products. A basic knowledge of starch characteristics and storage process is required to improve cassava starch quality and quantity. This report describes a comparative study of morphology, starch granule size distribution and amylose content in cassava storage roots grown under different conditions. Microscopic evaluation reveals that storage roots contain larger starch granules than fibrous roots. The study on three Asian cassava cultivars demonstrates the increment of starch granule size from outermost to innermost layers of storage root, while no significant change is observed in amylose content. The effects of developmental stage and growing season on cassava starch reveals that granule size is significantly influenced by both factors, while the amylose contents only fluctuate in a narrow range. The size of the starch granules increases particularly in the first six months after cultivation. Planting cassava in the beginning of the wet season in Asia yields larger granule sizes than planting in the dry season. The significance of this study lies in better understanding optimal growing conditions for improved starch characteristics and production, leading to a better quality agricultural production of this important food and materials crop.     

Cyanogen content of cassava roots and flour in Indonesia

A survey has been made of the total cyanogen content of cassava roots and products from the cassava growing provinces of Lampung and East, Central and West Java, in Indonesia. Twenty five samples of cassava products were analysed for cyanogens by the acid hydrolysis method and also by the simple picrate kit method. The mean percentage difference between the results was 17%. Thirty samples of cassava starch and other specialised products had a mean cyanogen content of only 5 ppm, whereas 29 samples of cassava flour, chip and gaplek gave a much higher mean cyanogen content of 54 ppm (SD 51). The WHO safe value for cassava flour is 10 ppm and the Indonesian level is 40 ppm. There are four outliers of cyanogen content 140–200 ppm, which would be dangerous to human health. The cyanogen content of starch/chips/gaplek needs to be reduced by using cultivars of lower cyanogen content and by using improved processing methods. Twenty seven samples of cassava roots gave a mean cyanogen content of 19 ppm (SD 14). ©     

木薯生料发酵制备燃料乙醇的工艺条件研究

试验对木薯生料发酵制备乙醇的工艺条件进行了优化研究,对影响发酵过程的生料淀粉水解酶用量、料液比、发酵初始pH和发酵温度四个因素在单因素试验的基础上进行了正交试验优化,得到最佳发酵条件为生料水解酶用量4 mL/kg,料液比1∶3.5,初始pH4.5,发酵温度37℃,根据优化条件进行验证试验,总糖消耗率与淀粉利用率分别为83.29%和79.80%,但与低温水解发酵工艺相比尚有一段距离。     

糖型与淀粉型木薯后代块根品质与发酵特性

为了研究糖型与淀粉型木薯后代块根品质与发酵特性,测定了28个木薯品系块根的干物质、淀粉、总糖、还原糖、粗蛋白和灰分等主要品质性状。结果表明,淀粉型木薯后代块根的淀粉（14.52%）、总糖（27.48%）、干物质（41.24%）、粗蛋白（1.67%）和灰分（0.25%）含量,总体上比糖型木薯后代块根高;糖型木薯后代块根还原糖含量（2.01%）显著高于淀粉型木薯后代块根（0.61%）（P＜0.05）,而其淀粉含量仅6.62%。相关分析表明,还原糖与淀粉、总糖、干物质和粗蛋白等性状均呈显著负相关（P＜0.05）。通过杂交改良克服负相关,新品系SM03块根的乙醇转化率达到53.7 mL/100 g干质量,产酒精34.73 L/hm2。SM03和SC16只糖化、不经过糊化预处理,酵母发酵分别产酒精31.13 L/hm2、27.80 L/hm2,均是很有推广价值的能源木薯新品种。     

木薯酒精废醪液处理工艺研究进展

木薯是现阶段一种经济上可行、可以规模种植的酒精生产非粮原料,其发展潜力较大,但木薯酒精生产过程中产生的废醪液是一种高浓度的有机废水,处理难度大,一定程度上制约着木薯酒精产业的发展。对木薯酒精废醪液处理工艺中多采用的清液厌氧一好氧工艺及全糟厌氧一好氧工艺的生产现状及存在的问题进行了分析,并对以厌氧污泥回用、好氧污泥改性零排放等为特征的全糟厌氧清液协同处理工艺的应用状况进行了评述。     

醇酸降解淀粉制备糊精的研究

采用醇酸水解大米淀粉、高直链玉米淀粉和木薯淀粉,发现：在相同条件下,正丁醇-盐酸水解的木薯淀粉溶解性最大,且在水解3 d后无显著增加。因此,从颗粒结构、晶体结构和分子结构等方面系统地研究醇酸降解木薯淀粉制备糊精过程。经正丁醇-盐酸水解后,木薯淀粉颗粒破坏程度严重,且随水解时间的增加,大部分木薯淀粉颗粒均失去了原有的颗粒形状;经正丁醇-盐酸水解7 d后,木薯淀粉的粒径下降了42.0%。X-射线衍射结果表明正丁醇-盐酸水解木薯淀粉在2θ为20°处出现了衍射峰,证明淀粉在正丁醇-盐酸水解过程中形成了直链淀粉-正丁醇络合物。高效分子排阻色谱和淀粉-碘全波长扫描分析表明：木薯淀粉经过正丁醇-盐酸水解后分子量在4 h内急剧下降,水解4 h后下降趋势减缓,水解3 d后分子量无显著变化并趋于稳定。上述结果表明,采用正丁醇-盐酸水解木薯淀粉3 d为制备糊精的最佳条件。     

微波-超声波辅助制备木薯淀粉纳米颗粒及其特性表征

以广西特色资源木薯淀粉为原料,微波超声波辅助制备了木薯淀粉纳米颗粒。采用动态光散射技术考察了淀粉乳浓度、微波超声波处理功率、微波超声波处理时间、料醇比(淀粉溶液与乙醇体积比)、淀粉溶液的滴加速率、滴加淀粉溶液的过程中微波超声波功率对纳米颗粒尺寸及多分散系数(PDI)的影响,获得了制备木薯淀粉纳米颗粒的最优条件:淀粉乳浓度20 mg/mL,微波超声波处理功率为24:500 W:W,微波超声波处理时间是50 min,料醇比1:8,淀粉溶液的滴加速率是20 mL/min,滴加淀粉溶液过程中微波超声波功率为24:300 W:W。通过傅里叶红外光谱、场发射扫描电子显微镜、X-射线衍射仪对木薯原淀粉和最优条件下合成的木薯淀粉纳米颗粒进行了表征。研究了淀粉纳米颗粒的溶解度、溶胀度、吸水率、吸油率等理化性质。结果表明,木薯淀粉纳米颗粒球形形貌较好,尺寸分布较均一。晶型由A型变为V型,相对结晶度明显降低。与木薯原淀粉相比,淀粉纳米颗粒的溶解度由0.9%提高到78.3%、溶胀度由4.166%提高到10.86%、吸油率提高了170%、12 h内的吸水率提高了3.1%,分散性实验表明木薯淀粉纳米颗粒在水溶液中的分散性较好。该淀粉纳米颗粒可用于食品色素、香料、调味料、维生素、油脂等产品中,应用价值较高。     

酶法制备木薯微孔淀粉的工艺优化

为了优化包埋粉末油脂的木薯微孔淀粉工艺、提高吸附性能,利用糖化酶和α- 淀粉酶对木薯淀粉进行处理,先通过六组单因素试验确定反应时间、反应温度、pH 值、底物浓度、酶浓度以及糖化酶和α- 淀粉酶配比最佳范围,再通过L18(37)正交试验,研究这些因素对木薯微孔淀粉吸附性能的影响。结果表明,当反应时间7h、温度60℃、pH6.0、底物浓度40%、酶浓度2.5%、糖化酶和α- 淀粉酶配比为1:4(m/m)时制备的木薯微孔淀粉的吸附性能最佳,木薯微孔淀粉对油脂的吸附性与原淀粉相比,从11.5% 提高到52%,提高了4.52 倍。     

用于微生物油脂发酵的木薯淀粉水解工艺的优化

为了提高木薯淀粉的发酵产脂能力,采用正交实验和均匀设计法对木薯淀粉酶法水解工艺进行了优化,结果表明α-淀粉酶量、糖化酶量和液化温度对木薯淀粉水解有显著影响。当淀粉酶量为756 U/g,糖化酶量为602 U/g,液化温度为92°C,其水解DE值达到97.3%。以该水解液进行皮状丝胞酵母B3(T.cutaneum B3)油脂发酵时,其生物量和油脂产量分别为16.38 g/L和7.22 g/L,比葡萄糖作为碳源的生物量和油脂产量高46.25%和41.12%,利用木薯淀粉水解液作为新型发酵碳源生产微生物油脂是一种理想的途径。     

The effects of variety,drying procedure,fineness of grinding and dietary inclusion level on the bioavailability of Cassava (Manihot esculenta crantz) starch

The bioavailability of raw cassava starch from dried, whole roots, as affected by a number of variables, both inherent and processing-induced, was determined in a series of feeding trials using the rat as a test animal. Apparent starch digestibility was in excess of 99% and was unaffected by cassava variety, cyanide content, drying process, fineness of grinding, dietary inclusion level (up to 50% of the diet) and age of the animal. A high level of residual cyanide (406.6 mg kg^?1 dried cassava chips) reduced feed intake and weight gain. Since the floor-drying procedure, whilst effectively reducing the cyanide to an acceptable level, was without effect on the digestibility of cassava starch, it is recommended that this process be adopted for drying high cyanide cultivars of cassava destined for the animal feed market. This will allow cassava to be incorporated in the diet at a higher inclusion level with no undesirable effects on animal performance.     

Twin-Screw Extrusion as a Continuous Pretreatment Process for the Enzymatic Hydrolysis of Cassava

Twin-screw extrusion was evaluated as a pretreatment for the enzymatic hydrolysis of cassava starch to glucose. Extrusion temperature and pH affected the key parameters associated with the enzymatic hydrolysis of starch such as the water solubility index, the water absorption index, the apparent viscosity, and the susceptibility of the extruded starch to glucoamylase. The glucose concentration of extruded and enzyme-hydrolyzed cassava starch was approximately 5% greater than that of acid-liquefied and enzyme-hydrolyzed cassava starch.     

An efficient treatment for detoxification process of cassava starch by plant cell wall-degrading enzymes

The objective of this work was to remove linamarin in starch from cassava (Manihot esculenta Crantz cv. KU-50) roots, a high-cyanogen variety by using plant cell wall-degrading enzymes, xylanase and cellulase. The combination of xylanase from Bacillus firmus K-1 and xylanase and cellulase from Paenibacillus curdlanolyticus B-6 at the ratio of 1:9 showed the maximum synergism at 1.8 times for hydrolyzing cassava cortex cell walls and releasing linamarase. Combined enzyme treatment enhanced linamarin liberation from the parenchyma by 90%. In addition, when the combined enzymes were applied for detoxification during cassava starch production, a low-cyanide-product was obtained with decreased linamarin concentration (96%) compared to non-enzyme treated tissues. Based on these results, xylanase and cellulase treatment is a good method for low-cyanide-cassava starch production and could be applied for detoxification of cassava products during processing.     

酿酒活性干酵母生理特性的研究

建立一种酿酒活性干酵母生理活性的简易评价方法,比较并筛选一株适合以木薯粉水解液发酵发酵生产燃料酒精的活性干酵母。优化2株酿酒活性干酵母的活化条件、生长温度和生长pH值,以木薯粉水解液为发酵液,在最适生长条件下比较两株酵母的生长曲线、发酵强度、耐糖能力、耐温能力和耐酒精能力。选择酿酒活性干酵母Ⅰ作为木薯粉水解液发酵酵母,该酵母在前36h发酵强度高于1g(/L.h),36h后发酵强度迅速下降;耐糖能力为20%,耐受温度是55℃以及耐酒精浓度是7%。     

Comparative production of glucose and high fructose syrup from cassava and sweet potato roots by direct conversion techniques

High fructose syrup (HFS) is a highly valued liquid sweetener for beverage, confectionery and processed food industry, owing to its special attributes like high solubility and non-crystalline nature. Even though 85% HFS production is from corn, increased food demand has necessitated the search for alternative substrates and starchy root crops like cassava and sweet potato are potential raw materials. However, the economic production needs direct use of the roots and simplification of the cost-intensive steps. This study aims at the direct enzymatic conversion of roots for HFS production. Glucose yield was compared from six treatment systems viz., liquezyme–dextrozyme (T1), Stargen (T2), Stargen in two split doses (T3), Spezyme–Stargen (T4), Stargen (60 °C;T5) and Spezyme–Stargen (60 °C; T6). Glucose was higher (22–25%) from cassava than sweet potato (14.0–15.7%), owing to the high starch content in cassava. Conversion to glucose was higher in T1–T4 (95–98%) compared to 88–92% for T5 and T6. Although the fructose yield was more from cassava (8.36–9.78%) than sweet potato (5.2–6.0%), percentage conversion was similar (37–38%) for both the roots. The cost of production of HFS could be reduced by the direct hydrolysis of root slurry using Stargen.

Industrial relevance

The conventional process for HFS production involved three cost-intensive enzyme steps such as liquefaction, saccharification and isomerization and the major raw material is starch. Economic production using cheaper raw materials and simplification of the process are the decisive factors for the widespread use of HFS in the developing and less developed countries. The present study aimed at the direct conversion of cassava and sweet potato root slurry (without conversion to starch) through the use of improved enzymes like Spezyme and Stargen and mild operating conditions of pH and temperature. The cost of production of HFS could be reduced by using the wet root slurry and performing the Stargen aided saccharification at room temperature, followed by isomerization at 60 °C using Sweetzyme T.     

Selection and Characterization of Endomycopsis fibuligera Strains for One-step Fermentation of Starch to Ethanol

In a step-wise systematic selection, a strain of Endomycopsis fibuligera NRRL 76 was found to be better than the other strains tested in the production of α-amylase and glucoamylase as well as ethanol directly from sugary and starchy substrates. Comparatively, the strain tolerated more ethanol. converted more starch to ethanol, produced less biomass and did not assimilate ethanol. There was an interrelationship between qualitative and quantitative production of amylases and ethanol production in batch fermentation with various strains. The constitutive nature of glucoamylase produced. Us lack of catabo-lite repression and resistance to ethanol inhibition as well as the nature of starch hydrolytic products obtained, appeared to be important characteristic features in the strain for efficient conversion of starch directly to ethanol. Among a wide range of starchy substrates used in ethanol production by the yeast strains, cassava starch and waxy rice were found to be more suitable. When the strain NRRL 76 was grown optimally at pH 6.0 and 30C for 1 d under aeration followed by 3d without aeration, the maximum ethanol concentration was 92.0g/L and 73.5 g/L in media containing 300g/L and 200g/L of cassava starch respectively as compared to 73.5g/L and 77.3g/L of ethanol by another promising strain of Schwanniomyces castellii ATCC 26077, under similar set of conditions. This process of NRRL 76 was compared with other one step processes reported in literature and found to be better than the others. The strain also converted high concentrations of cassava starch (up to 400g/L) and also waxy rice (250g/L) to ethanol satisfactorily.     

THE EFFECT OF FERMENTATION ON CASSAVA STARCH MICROSTRUCTURE

The effect of glucose syrup addition on sour cassava starch fermentation was studied on cassava starch from three locations in Santa Catarina State (Brazil), following four treatments: traditional, 0.10, 0.25 and 0.50% of glucose syrup added to total cassava suspension volume. A glucose syrup concentration of 0.50% contributed to doubling fermentation yield. The objective of this work was to observe the effect of the cassava starch fermentation process on starch granule microstructure, as compared with industrial processing. Micrography was performed using a scanning electron microscope, at 2000× magnification. Fermentations with 0.50% glucose syrup presented the greatest effects on starch granule microstructure.     

微波法制备硬脂酸木薯淀粉酯

目的建立微波辅助技术制备硬脂酸木薯淀粉酯,并对其理化性质进行表征。方法以木薯淀粉为原料,以硬脂酸为酯化剂,以盐酸为催化剂,通过均匀设计实验并经SPSS 10.0软件优化微波法制备硬脂酸木薯淀粉酯的最佳工艺参数。结果硬脂酸木薯淀粉酯的最佳工艺条件如下:淀粉50 g(干基),微波功率450 W,微波辐射时间1.5 min,盐酸加入量6.0 mL,硬脂酸0.5 g,得到的产品取代度为0.01685。结论本研究建立了一种无污染、反应快、能耗低的硬脂酸木薯淀粉酯制备方法,得到的产品取代度较高,溶解度、乳化性和乳化稳定性均优于原淀粉。     

Cassava Starch Technology: The Thai Experience

Cassava starch is an important export commodity of Thailand, about 2 × 10⁶ t are expected annually. Initially, cassava was mainly processed to meal and flour. Due to the high market demand for cassava products, the Thai cassava starch industry was established and has developed from small to large‐scale with improved processing technology. At present, a production capacity of one factory is, on average, 200 t starch per day. Transition from small to large‐scale production was accompanied by varietal development of root having high starch yield and technological improvement of starch production with shorter processing time and better starch quality. Most process technologies are still imported and adopted from those of other starches. The Thai cassava starch industry still encounters impediments, including high production cost, high resource consumption, starch loss, and adverse environmental impact especially sulfur, cyanide, solid and liquid waste. This industry continues to develop, in order to remain internationally competitive.     

The effect of pre‐harvest pruning of cassava upon root deterioration and quality characteristics

One of the major constraints of cassava as a crop is its perishability. Physiological deterioration, parenchymal blue–black vascular streaking, often starts within 24 h after harvest. This paper presents the results of a detailed study of the effects of pre‐harvest pruning upon post‐harvest physiological deterioration (PPD) and some other quality characteristics. Six cultivars, grown at CIAT (Centro International de Agricultura Tropical), with varying intrinsic susceptibility to PPD, were assessed at pruning–harvest intervals of 0, 2, 4, 6, 8, 10, 15, 20, 25, 28 and 39 days. After harvesting, the roots were analysed. For the unpruned plants a low susceptibility was found to coincide with a low dry matter content and a high sugar content. After pruning, the susceptibility for all cultivars was drastically reduced, reaching a minimum of around 25% of the original value for a pruning–harvest interval of up to 25 days. Beyond this interval the plants slowly develop new leaf canopy, normal assimilation sets in again and the starch content increases. Analysis of the cassava roots revealed a relationship between the combined sugar and starch contents and the interval duration, and that sugar and starch contents were inversely related to each other. The sugar content increased with the interval period, probably as a result of starch hydrolysis. Other properties such as the contents of dry matter, cyanogen, scopoletin, amylose and reducing sugars and the starch pasting properties were not affected by pruning to a comparable, interval‐dependent, extent. It is concluded that the sugar content, ie the sugar/starch ratio, of cassava roots is positively related to their resistance to post‐harvest physiological deterioration. © 2000 Society of Chemical Industry