食品廃棄物の処理方法として，好気性生ごみ溶解槽と二相式メタン発酵法を組み合わせたシステムと，エタノール固体発酵システムを考案した。メタン発酵システムは，190日間の連続運転から，生ごみ溶解槽の容積負荷は80～100kg-garbage/（m3・day），二相式メタン発酵法の酸生成槽は水理学的滞留時間（HRT）＝1.2 day，メタン発酵槽（EGSB）の容積負荷は9kgCOD/（m3・day）で運転できることがわかった。メタン発酵槽で回収されるメタンガス量は，生ごみ100 kgから5.8m3 Nであり，理論値の55%であった。システム全体のHRTが短く，処理水の下水道への放流が可能な点から，単相式メタン発酵法と比較して，有利であると考えられた。PCR-DGGE法により細菌相を調べた結果，生ごみ溶解槽と酸生成槽では微生物の機能がそれぞれ分離成立し，各槽の細菌間では共代謝していることが確認された。 エタノール固体発酵システムは，試料調製（水分調製），糖化発酵，蒸留の工程から構成される。乾燥生ごみにおいて糖化酵素の生産に適した麹菌として，麦味噌用のAspergillus oryzaeKBN650株を選出した。本菌株の乾燥生ごみにおける糖化酵素力の発現は，培養温度30℃，初発水分含量50%が最適であった。また，乾燥生ごみのエタノール固体発酵に適した酵母として，焼酎酵母Saccharomyces cerevisiae A30株を選出した。本菌株は，初発水分含量60%において高いエタノール生成能を示した。エタノール固体発酵システムでは，生ごみ150kgから，30℃，4日間の糖化発酵で，99%エタノール換算で6.2kgのエタノールが生産され，全糖消費量に対するエタノール回収率は70.0%であった。

We developed a new system to treat food waste and garbage using a two-phase methane fermentation system (TPMFS) with aerobic solubilization process (ASP) and ethanol solid-state fermentation system (ESSFS). In a continuous 190-day experiment using TPMFS, we found that ASP was able to convert a volumetric load of 80 to 100kg-garbage/(m3・day) and acidification process (AP) was able to operate at a hydraulic retention time (HRT) of 1.2 days. Additionally, the maximum volumetric load of methane fermentation process in an expanded granular sludge bed reactor (EGSB) was 9 kg-chemical oxygen demand (COD)/(m3・day). The advantages of TPMFS in comparison to those of single-phase MFS are the shortening of HRT and creating the possibility to discharge the treated water into the sewer system. As a result of investigating the microflora using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method, we found that the microbes in ASP varied compared to those in AP. Moreover, it was confirmed that co-metabolism existed among the microbes during ASP. ESSFS was constructed by including the sequential processes of material preparation (water content adjustment), multi parallel fermentation (saccharification and fermentation), and distillation. Based on properties such as the saccharifying enzyme productivity and ability to grow on dry food waste, Aspergillus oryzae KBN650, which is used for Japanese barley miso production, was selected as the most suitable mold for saccharification. The optimal conditions for the saccharifying enzyme productivity in this strain were a cultivation temperature of 30℃and initial water content (IWC) of 50%. Further, Saccharomyces cerevisiae A30, which is used for shochu production, was selected as the most suitable yeast for ESSFS. The maximum ethanol productivity of this strain was observed at an IWC of 60%. In TPMFS, saccharification and fermentation at 30℃for 4 days produced ethanol (6.2kg; 99% purity) from food waste (150kg). The ethanol recovery rate was 70.0% based on the amount of consumption of all the sugars.

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