An Economical Method for Simultaneously Improving Pretreatment and Anaerobic Fermentation Effects on Corn Straw Using Ultra-Low Concentration FeCl2

Low pollution, slight corrosion, and low cost are the main challenges in the conversion of biomass to biogas. In this work, based on the whole process optimization of biomass conversion, an effective method using an ultra-low concentration of FeCl2 was proposed to simultaneously promote the biochemical reaction and improve the pretreatment effect. The concentration of FeCl2 in the pretreatment was determined according to the requirements of the minimum amount which led to the optimal performance of the anaerobic system and had economical importance. The effects of FeCl2 in the pretreatment and anaerobic fermentation were evaluated by comparing with that of distilled water in the production of hydrolysis products and organic acids. The optimal condition was obtained at 180 °C and 10 min with 1 × 10−5 mol/L FeCl2 pretreatment. At that condition, hemicellulose achieved a high conversion of 97.6%, and the released xylose reached nearly 95%. At least 77.5% of the organic matter in the solution can be utilized for subsequent fermentation. FeCl2 pretreatment also accelerated the anaerobic acidification fermentation process and promoted organic acid yields. The work provided a meaningful and economical choice for the conversion technology of biomass to biogas.

The effect of ensiling and alkaline pretreatment on anaerobic acidification of Napier grass in the leached bed process

The characteristics of feedstock are important to the biocatalyst-based processes. Herein the effect of ensiling and alkaline pretreatment on acidification of Napier grass in anaerobic leached bed reactors was investigated. The results depicted clearly that grass preparation affected its chemical properties and leaching ability differently. After pretreatment in 3.0% of NaOH, lignin was reduced significantly by 50.1% to 68.0%, while less deterioration was found for ensiling. About 18.9% to 54.1% of the produced soluble chemical oxygen demand (SCOD) of these biomasses was increased subsequently compared to 0.102 kg SCOD or 0.56 kg SCOD/kg VS_added of raw grass digestion. However, about 3.3% of SCOD was reduced after the ensiling. An extension of biomass soaking time and heat supplementation under alkali-thermal conditions of raw grass promoted more production of SCOD for 18.9% to 29.9% and 54.1%, respectively. While about 45.5% to 54.4% of SCOD was increased for alkali-thermal pretreated residue. The solid content and lignocelluloses were changed differently and accordingly with treatment conditions. Similar profiles of leachates contained mainly acetic acid were obtained. These results confirm the beneficial application of alkaline soaking and ensiling as a pretreatment method to enhance the solubilization of grass biomass under the leached bed acidification process.

Determination of Glucose Concentration in Anaerobic Acidification Cultures by Portable Glucose Monitoring System

In mixed microbial fermentation, sugar concentration should be monitored regularly in order to evaluate the effectiveness of fermentation process. Anaerobic acidification fermentation is the process involving microbes to convert the soluble carbohydrate (e.g. glucose) derived from the hydrolysis of insoluble carbohydrates (e.g. starch). The determination of glucose during the fermentation is essential in order to evaluate the mass balance of electron transfer from the oxidation of glucose to the fermentation end-products (e.g. organic acids and alcohols). The fast and practical measurements of glucose concentration in the fermentation broth are highly required to evaluate and ensure the stability of fermentation process. The results showed that once glucose as a soluble sugar is available in the fermentation broth, it was accurately measured by GlucoDr blood glucose biosensor. The standard curve of glucose solution showed the linear relationship between glucometer reading and glucose concentration in which the coefficient determination obtained was at about 0.99. This indicated that glucose analysis with using GlucoDr blood glucose biosensor was accurate and reproducible.

Anaerobic Acidification of Coconut Water Waste by Lactobacillus acidophilus Culture for Biotechnological Production of Lactic Acid

The biotechnological production of lactic acid could be carried out via anaerobic acidification process. In order to achieve an optimal production of lactic acid, the role of inoculum would be essential. The current study aimed to investigate as well as evaluate the effect of inoculum concentration on the anaerobic acidification of coconut water waste for the production of lactic acid. Results showed that the addition of 20% inoculums to the reactor fermenting coconut water waste was sufficient for the optimal production of lactic acid. In the batch process anaerobic acidification of coconut water waste inoculated with 20% inoculums of Lactobacillus acidophilus culture had the yield of lactic acid production, which was about 1.62 mmol lactic acid/mmol glucose while under the continuous operation the yield of lactic acid production obtained, was about 1.15 mmol lactic acid/mmol glucose. During the acidification process in both batch and continuous modes pH dropped significantly from 5.1 to 3.7.